@Article{Erskine2018,
  Title                    = {Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed},
  Author                   = {Erskine, J. and England, D. and Kupchak, C. and Sussman, B.},
  Journal                  = {Optics Letters},
  Year                     = {2018},
  Number                   = {4},
  Pages                    = {907--910},
  Volume                   = {43},

  __markedentry            = {[paul:]},
  Abstract                 = {Photon pair sources have wide ranging applications in a variety of quantum photonic experiments and protocols. Many of these protocols require well controlled spectral correlations between the two output photons. However, due to low cross-sections, measuring the joint spectral properties of photon pair sources has historically been a challenging and time-consuming task. Here, we present an approach for the real-time measurement of the joint spectral properties of a fiber-based four wave mixing source. We seed the four wave mixing process using a broadband chirped pulse, studying the stimulated process to extract information regarding the spontaneous process. In addition, we compare stimulated emission measurements with the spontaneous process to confirm the technique{\textquoteright}s validity. Joint spectral measurements have taken many hours historically and several minutes with recent techniques. Here, measurements have been demonstrated in 5--30 s depending on resolution, offering substantial improvement. Additional benefits of this approach include flexible resolution, large measurement bandwidth, and reduced experimental overhead. {\copyright} 2018 Optical Society of America.},
  Affiliation              = {Department of Physics, University of Ottawa, 598 King Edward, Ottawa, ON, Canada; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada},
  Document_type            = {Article},
  Doi                      = {10.1364/OL.43.000907},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042081705&doi=10.1364%2fOL.43.000907&partnerID=40&md5=d836eddded287aa89aedf00ac3d34488}
}

Photon pair sources have wide ranging applications in a variety of quantum photonic experiments and protocols. Many of these protocols require well controlled spectral correlations between the two output photons. However, due to low cross-sections, measuring the joint spectral properties of photon pair sources has historically been a challenging and time-consuming task. Here, we present an approach for the real-time measurement of the joint spectral properties of a fiber-based four wave mixing source. We seed the four wave mixing process using a broadband chirped pulse, studying the stimulated process to extract information regarding the spontaneous process. In addition, we compare stimulated emission measurements with the spontaneous process to confirm the technique\textquoterights validity. Joint spectral measurements have taken many hours historically and several minutes with recent techniques. Here, measurements have been demonstrated in 5–30 s depending on resolution, offering substantial improvement. Additional benefits of this approach include flexible resolution, large measurement bandwidth, and reduced experimental overhead. © 2018 Optical Society of America.

@Conference{Erskine2018a,
  Title                    = {Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed},
  Author                   = {Erskine, J. and England, D.G. and Kupchak, C. and Sussman, B.J.},
  Year                     = {2018},
  Volume                   = {Part F93-CLEO_QELS 2018},

  __markedentry            = {[paul:]},
  Abstract                 = {We perform joint spectral intensity measurements by studying stimulated four wave mixing in a birefringent fiber photon pair source. Seeding the process with a chirped supercontinuum beam, measurements are acquired in as little as 5 s. {\copyright} OSA 2018.},
  Affiliation              = {National Research Council, Ottawa, Canada; Department of Physics, University of Ottawa, Ottawa, Canada},
  Document_type            = {Conference Paper},
  Doi                      = {10.1364/CLEO_QELS.2018.FM4G.6},
  Journal                  = {Optics InfoBase Conference Papers},
  Page_count               = {2},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048935944&doi=10.1364%2fCLEO_QELS.2018.FM4G.6&partnerID=40&md5=79b6888893bc3a7972ae24409ae1b063}
}

We perform joint spectral intensity measurements by studying stimulated four wave mixing in a birefringent fiber photon pair source. Seeding the process with a chirped supercontinuum beam, measurements are acquired in as little as 5 s. © OSA 2018.

@Article{Forbes2018,
  Title                    = {{Quantum-beat photoelectron-imaging spectroscopy of Xe in the VUV}},
  Author                   = {Forbes, Ruaridh and Makhija, Varun and Underwood, Jonathan G. and Stolow, Albert and Wilkinson, Iain and Hockett, Paul and Lausten, Rune},
  Journal                  = {Physical Review A},
  Year                     = {2018},

  Month                    = jun,
  Number                   = {6},
  Pages                    = {063417},
  Volume                   = {97},

  __markedentry            = {[paul:]},
  Abstract                 = {Time-resolved pump-probe measurements of Xe, pumped at 133{\~{}}nm and probed at 266{\~{}}nm, are presented. The pump pulse prepared a long-lived hyperfine wavepacket, in the Xe {\$}5p{\^{}}5({\^{}}2P{\^{}}{\{}\backslashcirc{\}}{\_}{\{}1/2{\}})6s{\~{}}{\^{}}2[1/2]{\^{}}{\{}\backslashcirc{\}}{\_}1{\$} manifold ({\$}E={\$}77185 cm{\$}{\^{}}{\{}-1{\}}={\$}9.57 eV). The wavepacket was monitored via single-photon ionization, and photoelectron images measured. The images provide angle- and time-resolved data which, when obtained over a large time-window (900{\~{}}ps), constitute a precision quantum beat spectroscopy measurement of the hyperfine state splittings. Additionally, analysis of the full photoelectron image stack provides a quantum beat imaging modality, in which the Fourier components of the photoelectron images correlated with specific beat components can be obtained. This may also permit the extraction of isotope-resolved photoelectron images in the frequency domain, in cases where nuclear spins (hence beat components) can be uniquely assigned to specific isotopes (as herein), and also provides phase information. The information content of both raw, and inverted, image stacks is investigated, suggesting the utility of the Fourier analysis methodology in cases where images cannot be inverted.},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1803.01081},
  Doi                      = {10.1103/PhysRevA.97.063417},
  Eprint                   = {1803.01081},
  ISSN                     = {2469-9926},
  Timestamp                = {2018.07.12},
  Url                      = {http://arxiv.org/abs/1803.01081}
}

Time-resolved pump-probe measurements of Xe, pumped at 133\ nm and probed at 266\ nm, are presented. The pump pulse prepared a long-lived hyperfine wavepacket, in the Xe $}5p{^}5({^}2P{^}{\{}i̧rc{\}}{_}{\{}1/2{\}})6s{\ {}}{^}2[1/2]{^}{\{}i̧rc{\}}{_}1{$ manifold ($}E={$77185 cm$}{^}{\{}-1{\}}={$9.57 eV). The wavepacket was monitored via single-photon ionization, and photoelectron images measured. The images provide angle- and time-resolved data which, when obtained over a large time-window (900\ ps), constitute a precision quantum beat spectroscopy measurement of the hyperfine state splittings. Additionally, analysis of the full photoelectron image stack provides a quantum beat imaging modality, in which the Fourier components of the photoelectron images correlated with specific beat components can be obtained. This may also permit the extraction of isotope-resolved photoelectron images in the frequency domain, in cases where nuclear spins (hence beat components) can be uniquely assigned to specific isotopes (as herein), and also provides phase information. The information content of both raw, and inverted, image stacks is investigated, suggesting the utility of the Fourier analysis methodology in cases where images cannot be inverted.

@Book{Hockett2018,
  Title                    = {{Quantum Metrology with Photoelectrons, Volume 2 {A}pplications and advances}},
  Author                   = {Hockett, Paul},
  Publisher                = {IOP Publishing},
  Year                     = {2018},

  __markedentry            = {[paul:]},
  Comment                  = {Website: https://osf.io/q2v3g},
  Doi                      = {10.1088/978-1-6817-4688-3},
  ISBN                     = {978-1-6817-4688-3},
  Timestamp                = {2018.07.12},
  Url                      = {http://iopscience.iop.org/book/978-1-6817-4688-3}
}

@Book{Hockett2018a,
  Title                    = {{Quantum Metrology with Photoelectrons, Volume 1 {F}oundations}},
  Author                   = {Hockett, Paul},
  Publisher                = {IOP Publishing},
  Year                     = {2018},

  __markedentry            = {[paul:]},
  Comment                  = {Website: https://osf.io/q2v3g},
  Doi                      = {10.1088/978-1-6817-4684-5},
  ISBN                     = {978-1-6817-4684-5},
  Timestamp                = {2018.07.12},
  Url                      = {http://iopscience.iop.org/book/978-1-6817-4684-5}
}

@Article{Bustard2017,
  Title                    = {Quantum frequency conversion with ultra-broadband tuning in a Raman memory},
  Author                   = {Bustard, P.J. and England, D.G. and Heshami, K. and Kupchak, C. and Sussman, B.J.},
  Journal                  = {Physical Review A},
  Year                     = {2017},
  Number                   = {5},
  Volume                   = {95},

  __markedentry            = {[paul:]},
  Abstract                 = {Quantum frequency conversion is a powerful tool for the construction of hybrid quantum photonic technologies. Raman quantum memories are a promising method of conversion due to their broad bandwidths. Here we demonstrate frequency conversion of THz-bandwidth, fs-duration photons at the single-photon level using a Raman quantum memory based on the rotational levels of hydrogen molecules. We shift photons from 765 nm to wavelengths spanning from 673 to 590 nm - an absolute shift of up to 116 THz. We measure total conversion efficiencies of up to 10% and a maximum signal-to-noise ratio of 4.0(1):1, giving an expected conditional fidelity of 0.75, which exceeds the classical threshold of 2/3. Thermal noise could be eliminated by cooling with liquid nitrogen, giving noiseless conversion with wide tunability in the visible and infrared. {\copyright} 2017 American Physical Society.},
  Affiliation              = {National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada; Department of Physics, University of Ottawa, Ottawa, ON, Canada},
  Art_number               = {053816},
  Document_type            = {Article},
  Doi                      = {10.1103/PhysRevA.95.053816},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026811427&doi=10.1103%2fPhysRevA.95.053816&partnerID=40&md5=bb46367e7043844ddf47d7922a010887}
}

Quantum frequency conversion is a powerful tool for the construction of hybrid quantum photonic technologies. Raman quantum memories are a promising method of conversion due to their broad bandwidths. Here we demonstrate frequency conversion of THz-bandwidth, fs-duration photons at the single-photon level using a Raman quantum memory based on the rotational levels of hydrogen molecules. We shift photons from 765 nm to wavelengths spanning from 673 to 590 nm - an absolute shift of up to 116 THz. We measure total conversion efficiencies of up to 10% and a maximum signal-to-noise ratio of 4.0(1):1, giving an expected conditional fidelity of 0.75, which exceeds the classical threshold of 2/3. Thermal noise could be eliminated by cooling with liquid nitrogen, giving noiseless conversion with wide tunability in the visible and infrared. © 2017 American Physical Society.

@Conference{England2017,
  Title                    = {A quantum light-matter beamsplitter in diamond},
  Author                   = {England, D.G. and Heshami, K. and Bustard, P.J. and Sussman, B.J. and Fisher, K.A.G. and MacLean, J.-P.W. and Resch, K.J.},
  Year                     = {2017},
  Volume                   = {Part F42-CLEO_QELS 2017},

  __markedentry            = {[paul:]},
  Abstract                 = {A quantum memory can be viewed as a light-matter beam-splitter, mapping a photon to a superposition of the output optical mode and stored mode. We use this mechanism to demonstrate non-classical onephoton and two-photon interference. {\copyright} OSA 2017.},
  Affiliation              = {National Research Council, Ottawa, Canada; Institute for Quantum Computing, University of Waterloo, Waterloo, Canada},
  Document_type            = {Conference Paper},
  Doi                      = {10.1364/CLEO_QELS.2017.FM2E.5},
  Journal                  = {Optics InfoBase Conference Papers},
  Page_count               = {2},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020685777&doi=10.1364%2fCLEO_QELS.2017.FM2E.5&partnerID=40&md5=54c164317411ed8771f8961504153465}
}

A quantum memory can be viewed as a light-matter beam-splitter, mapping a photon to a superposition of the output optical mode and stored mode. We use this mechanism to demonstrate non-classical onephoton and two-photon interference. © OSA 2017.

@Article{Fisher2017,
  Title                    = {Storage of polarization-entangled {THz}-bandwidth photons in a diamond quantum memory},
  Author                   = {Fisher, K.A.G. and England, D.G. and MacLean, J.-P.W. and Bustard, P.J. and Heshami, K. and Resch, K.J. and Sussman, B.J.},
  Journal                  = {Physical Review A},
  Year                     = {2017},
  Number                   = {1},
  Volume                   = {96},

  __markedentry            = {[paul:]},
  Abstract                 = {Bulk diamond phonons have been shown to be a versatile platform for the generation, storage, and manipulation of high-bandwidth quantum states of light. Here we demonstrate a diamond quantum memory that stores, and releases on demand, an arbitrarily polarized $\sim$250 fs duration photonic qubit. The single-mode nature of the memory is overcome by mapping the two degrees of polarization of the qubit, via Raman transitions, onto two spatially distinct optical phonon modes located in the same diamond crystal. The two modes are coherently recombined upon retrieval and quantum process tomography confirms that the memory faithfully reproduces the input state with average fidelity 0.784$\pm$0.004 with a total memory efficiency of (0.76$\pm$0.03)%. In an additional demonstration, one photon of a polarization-entangled pair is stored in the memory. We report that entanglement persists in the retrieved state for up to 1.3 ps of storage time. These results demonstrate that the diamond phonon platform can be used in concert with polarization qubits, a key requirement for polarization-encoded photonic processing. {\copyright} 2017 American Physical Society.},
  Affiliation              = {Institute for Quantum Computing, Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada; Department of Physics, University of Ottawa, Ottawa, ON, Canada; Department of Physics, Centre for Quantum Information and Quantum Control, Institute for Optical Sciences, University of Toronto, 60 St. George Street, Toronto, ON, Canada},
  Art_number               = {012324},
  Document_type            = {Article},
  Doi                      = {10.1103/PhysRevA.96.012324},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026832050&doi=10.1103%2fPhysRevA.96.012324&partnerID=40&md5=8e76ba081c99132fe77f96b2483e2bd5}
}

Bulk diamond phonons have been shown to be a versatile platform for the generation, storage, and manipulation of high-bandwidth quantum states of light. Here we demonstrate a diamond quantum memory that stores, and releases on demand, an arbitrarily polarized $∼$250 fs duration photonic qubit. The single-mode nature of the memory is overcome by mapping the two degrees of polarization of the qubit, via Raman transitions, onto two spatially distinct optical phonon modes located in the same diamond crystal. The two modes are coherently recombined upon retrieval and quantum process tomography confirms that the memory faithfully reproduces the input state with average fidelity 0.784$±$0.004 with a total memory efficiency of (0.76$±$0.03)%. In an additional demonstration, one photon of a polarization-entangled pair is stored in the memory. We report that entanglement persists in the retrieved state for up to 1.3 ps of storage time. These results demonstrate that the diamond phonon platform can be used in concert with polarization qubits, a key requirement for polarization-encoded photonic processing. © 2017 American Physical Society.

@Article{Forbes2017,
  Title                    = {Time-resolved multi-mass ion imaging: Femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera},
  Author                   = {Forbes, R. and Makhija, V. and Veyrinas, K. and Stolow, A. and Lee, J.W.L. and Burt, M. and Brouard, M. and Vallance, C. and Wilkinson, I. and Lausten, R. and Hockett, P.},
  Journal                  = {Journal of Chemical Physics},
  Year                     = {2017},
  Number                   = {1},
  Volume                   = {147},

  Abstract                 = {The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with (x, y) position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C2F3I photolysis are presented. The experiments utilized femtosecond VUV and UV (160.8 nm and 267 nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicate the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared. © 2017 Crown.},
  Art_number               = {013911},
  Document_type            = {Article},
  Doi                      = {10.1063/1.4978923},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017137986&doi=10.1063%2f1.4978923&partnerID=40&md5=ad133dc43109bff535caeaa6fd29d5d6}
}

The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with (x, y) position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C2F3I photolysis are presented. The experiments utilized femtosecond VUV and UV (160.8 nm and 267 nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicate the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared. © 2017 Crown.

@Article{Forbes2017a,
  Title                    = {{Time-resolved multi-mass ion imaging: Femtosecond {UV}-VUV pump-probe spectroscopy with the PImMS camera}},
  Author                   = {Forbes, Ruaridh and Makhija, Varun and Veyrinas, K{\'{e}}vin and Stolow, Albert and Lee, Jason W. L. and Burt, Michael and Brouard, Mark and Vallance, Claire and Wilkinson, Iain and Lausten, Rune and Hockett, Paul},
  Journal                  = {The Journal of Chemical Physics},
  Year                     = {2017},

  Month                    = jul,
  Number                   = {1},
  Pages                    = {013911},
  Volume                   = {147},

  __markedentry            = {[paul:]},
  Abstract                 = {The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with {\$}(x,y){\$} position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C{\$}{\_}2{\$}F{\$}{\_}3{\$}I photolysis are presented. The experiments utilized femtosecond UV and VUV (160.8{\~{}}nm and 267{\~{}}nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicates the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared.},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1702.00744},
  Doi                      = {10.1063/1.4978923},
  Eprint                   = {1702.00744},
  ISSN                     = {0021-9606},
  Timestamp                = {2018.07.12},
  Url                      = {http://arxiv.org/abs/1702.00744}
}

The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with $}(x,y){$ position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C$}{_}2{$F$}{_}3{$I photolysis are presented. The experiments utilized femtosecond UV and VUV (160.8\ nm and 267\ nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicates the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared.

@Article{Hockett2017b,
  Title                    = {{Angle-resolved RABBITT: theory and numerics}},
  Author                   = {Hockett, Paul},
  Journal                  = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  Year                     = {2017},

  Month                    = aug,
  Number                   = {15},
  Pages                    = {154002},
  Volume                   = {50},

  __markedentry            = {[paul:]},
  Abstract                 = {{\textcopyright} 2017 IOP Publishing Ltd. Angle-resolved (AR) RABBITT measurements offer a high information content measurement scheme, due to the presence of multiple, interfering, ionization channels combined with a phase-sensitive observable in the form of angle and time-resolved photoelectron interferograms. In order to explore the characteristics and potentials of AR-RABBITT, a perturbative 2-photon model is developed; based on this model, example AR-RABBITT results are computed for model and real systems, for a range of RABBITT schemes. These results indicate some of the phenomena to be expected in AR-RABBITT measurements, and suggest various applications of the technique in photoionization metrology.},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1703.08586},
  Doi                      = {10.1088/1361-6455/aa7887},
  Eprint                   = {1703.08586},
  ISSN                     = {0953-4075},
  Keywords                 = {angle-resolved,atto,photoelectron spectroscopy,photoionization,ultrafast},
  Timestamp                = {2018.07.12},
  Url                      = {http://stacks.iop.org/0953-4075/50/i=15/a=154002?key=crossref.5d6778123ace5e660772ac4533b801a0}
}

© 2017 IOP Publishing Ltd. Angle-resolved (AR) RABBITT measurements offer a high information content measurement scheme, due to the presence of multiple, interfering, ionization channels combined with a phase-sensitive observable in the form of angle and time-resolved photoelectron interferograms. In order to explore the characteristics and potentials of AR-RABBITT, a perturbative 2-photon model is developed; based on this model, example AR-RABBITT results are computed for model and real systems, for a range of RABBITT schemes. These results indicate some of the phenomena to be expected in AR-RABBITT measurements, and suggest various applications of the technique in photoionization metrology.

@Article{Hockett2017,
  Title                    = {Reply to Comment on 'Time delays in molecular photoionization'},
  Author                   = {Hockett, P. and Frumker, E. and Villeneuve, D.M. and Corkum, P.B.},
  Journal                  = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  Year                     = {2017},
  Number                   = {7},
  Volume                   = {50},

  Art_number               = {078003},
  Document_type            = {Letter},
  Doi                      = {10.1088/1361-6455/aa620c},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016145722&doi=10.1088%2f1361-6455%2faa620c&partnerID=40&md5=0ec8686c1f9399af585ca721b7fbf80c}
}

@Article{Khazali2017,
  Title                    = {Single-photon source based on Rydberg exciton blockade},
  Author                   = {Khazali, M. and Heshami, K. and Simon, C.},
  Journal                  = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  Year                     = {2017},
  Number                   = {21},
  Volume                   = {50},

  __markedentry            = {[paul:]},
  Abstract                 = {Bound states of electron-hole pairs in semiconductors demonstrate a hydrogen-like behavior in their high-lying excited states that are also known as Rydberg exciton states. The strong interaction between excitons in levels with high principal quantum numbers prevents the creation of more than one exciton in a small crystal; resulting in the Rydberg blockade effect. Here, we propose a new kind of solid-state single-photon source based on the recently observed Rydberg blockade effect for excitons in cuprous oxide. Our quantitative estimates based on single and double excitation probability dynamics indicate that GHz rates and values of the second-order correlation function g2 (0) below the percent level can be simultaneously achievable. These results should pave the way to explore applications of Rydberg excitons in photonic quantum information processing.},
  Affiliation              = {Institute for Quantum Science and Technology, Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada},
  Art_number               = {215301},
  Author_keywords          = {Rydberg blockade; Rydberg excitons; single-photon sources},
  Document_type            = {Article},
  Doi                      = {10.1088/1361-6455/aa8d7c},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032746181&doi=10.1088%2f1361-6455%2faa8d7c&partnerID=40&md5=6ddff869582040071c05e99ed42b32fd}
}

Bound states of electron-hole pairs in semiconductors demonstrate a hydrogen-like behavior in their high-lying excited states that are also known as Rydberg exciton states. The strong interaction between excitons in levels with high principal quantum numbers prevents the creation of more than one exciton in a small crystal; resulting in the Rydberg blockade effect. Here, we propose a new kind of solid-state single-photon source based on the recently observed Rydberg blockade effect for excitons in cuprous oxide. Our quantitative estimates based on single and double excitation probability dynamics indicate that GHz rates and values of the second-order correlation function g2 (0) below the percent level can be simultaneously achievable. These results should pave the way to explore applications of Rydberg excitons in photonic quantum information processing.

@Article{Kupchak2017,
  Title                    = {Time-bin-to-polarization conversion of ultrafast photonic qubits},
  Author                   = {Kupchak, C. and Bustard, P.J. and Heshami, K. and Erskine, J. and Spanner, M. and England, D.G. and Sussman, B.J.},
  Journal                  = {Physical Review A},
  Year                     = {2017},
  Number                   = {5},
  Volume                   = {96},

  __markedentry            = {[paul:]},
  Abstract                 = {The encoding of quantum information in photonic time-bin qubits is apt for long-distance quantum communication schemes. In practice, due to technical constraints such as detector response time, or the speed with which copolarized time-bins can be switched, other encodings, e.g., polarization, are often preferred for operations like state detection. Here, we present the conversion of qubits between polarization and time-bin encodings by using a method that is based on an ultrafast optical Kerr shutter and attain efficiencies of 97% and an average fidelity of 0.827$\pm$0.003 with shutter speeds near 1 ps. Our demonstration delineates an essential requirement for the development of hybrid and high-rate optical quantum networks. {\copyright} 2017 American Physical Society.},
  Affiliation              = {Department of Physics, University of Ottawa, Ottawa, ON, Canada; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada},
  Art_number               = {053812},
  Document_type            = {Article},
  Doi                      = {10.1103/PhysRevA.96.053812},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033582063&doi=10.1103%2fPhysRevA.96.053812&partnerID=40&md5=befc876df8ad61786431df849d8f9cbf}
}

The encoding of quantum information in photonic time-bin qubits is apt for long-distance quantum communication schemes. In practice, due to technical constraints such as detector response time, or the speed with which copolarized time-bins can be switched, other encodings, e.g., polarization, are often preferred for operations like state detection. Here, we present the conversion of qubits between polarization and time-bin encodings by using a method that is based on an ultrafast optical Kerr shutter and attain efficiencies of 97% and an average fidelity of 0.827$±$0.003 with shutter speeds near 1 ps. Our demonstration delineates an essential requirement for the development of hybrid and high-rate optical quantum networks. © 2017 American Physical Society.

@Article{Marceau2017,
  Title                    = {{Molecular Frame Reconstruction Using Time-Domain Photoionization Interferometry}},
  Author                   = {Marceau, Claude and Makhija, Varun and Platzer, Dominique and Naumov, A. Yu. and Corkum, P. B. and Stolow, Albert and Villeneuve, D. M. and Hockett, Paul},
  Journal                  = {Physical Review Letters},
  Year                     = {2017},

  Month                    = aug,
  Number                   = {8},
  Pages                    = {083401},
  Volume                   = {119},

  __markedentry            = {[paul:]},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1701.08432},
  Doi                      = {10.1103/PhysRevLett.119.083401},
  Eprint                   = {1701.08432},
  ISSN                     = {0031-9007},
  Publisher                = {American Physical Society},
  Timestamp                = {2018.07.12}
}

@Article{Sit2017,
  Title                    = {High-dimensional intracity quantum cryptography with structured photons},
  Author                   = {Sit, A. and Bouchard, F. and Fickler, R. and Gagnon-Bischoff, J. and Larocque, H. and Heshami, K. and Elser, D. and Peuntinger, C. and G{\"{u}}nthner, K. and Heim, B. and Marquardt, C. and Leuchs, G. and Boyd, R.W. and Karimi, E.},
  Journal                  = {Optica},
  Year                     = {2017},
  Number                   = {9},
  Pages                    = {1006--1010},
  Volume                   = {4},

  __markedentry            = {[paul:]},
  Abstract                 = {Quantum key distribution (QKD) promises information-theoretically secure communication and is already on the verge of commercialization. The next step will be to implement high-dimensional protocols in order to improve noise resistance and increase the data rate. Hitherto, no experimental verification of high-dimensional QKD in the single-photon regime has been conducted outside of the laboratory. Here, we report the realization of such a single-photon QKD system in a turbulent free-space link of 0.3 km over the city of Ottawa, taking advantage of both the spin and orbital angular momentum photonic degrees of freedom. This combination of optical angular momenta allows us to create a 4-dimensional quantum state; wherein, using a high-dimensional BB84 protocol, a quantum bit error rate of 11% was attained with a corresponding secret key rate of 0.65 bits per sifted photon. In comparison, an error rate of 5% with a secret key rate of 0.43 bits per sifted photon is achieved for the case of 2-dimensional structured photons. We thus demonstrate that, even through moderate turbulence without active wavefront correction, high-dimensional photon states are advantageous for securely transmitting more information. This opens the way for intracity high-dimensional quantum communications under realistic conditions. {\copyright} 2017 Optical Society of America.},
  Affiliation              = {Physics Department, Centre for Research in Photonics, University of Ottawa, Advanced Research Complex, 25 Templeton, Ottawa, ON, Canada; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada; Max-Planck-Institut f�r die Physik des Lichts, Staudtstra�e 2, Erlangen, Germany; Institut f�r Opti, Information und Photonik, Universit�t Erlangen-N�rnberg, Staudtstra�e 7/B2, Erlangen, Germany; Institute of Optics, University of Rochester, Rochester, NY, United States; Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran},
  Author_keywords          = {Free-space optical communication; Optical vortices; Quantum cryptography},
  Document_type            = {Article},
  Doi                      = {10.1364/OPTICA.4.001006},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029861458&doi=10.1364%2fOPTICA.4.001006&partnerID=40&md5=cc2fd01a976a7229c3f7ee2f141b021c}
}

Quantum key distribution (QKD) promises information-theoretically secure communication and is already on the verge of commercialization. The next step will be to implement high-dimensional protocols in order to improve noise resistance and increase the data rate. Hitherto, no experimental verification of high-dimensional QKD in the single-photon regime has been conducted outside of the laboratory. Here, we report the realization of such a single-photon QKD system in a turbulent free-space link of 0.3 km over the city of Ottawa, taking advantage of both the spin and orbital angular momentum photonic degrees of freedom. This combination of optical angular momenta allows us to create a 4-dimensional quantum state; wherein, using a high-dimensional BB84 protocol, a quantum bit error rate of 11% was attained with a corresponding secret key rate of 0.65 bits per sifted photon. In comparison, an error rate of 5% with a secret key rate of 0.43 bits per sifted photon is achieved for the case of 2-dimensional structured photons. We thus demonstrate that, even through moderate turbulence without active wavefront correction, high-dimensional photon states are advantageous for securely transmitting more information. This opens the way for intracity high-dimensional quantum communications under realistic conditions. © 2017 Optical Society of America.

@Article{Villeneuve2017,
  Title                    = {{Coherent imaging of an attosecond electron wave packet}},
  Author                   = {Villeneuve, D M and Hockett, Paul and Vrakking, M J J and Niikura, Hiromichi},
  Journal                  = {Science},
  Year                     = {2017},

  Month                    = jun,
  Number                   = {6343},
  Pages                    = {1150--1153},
  Volume                   = {356},

  __markedentry            = {[paul:]},
  Abstract                 = {Electrons detached from atoms or molecules by photoionization carry information about the quantum state from which they originate, as well as the continuum states into which they are released. Generally, the photoelectron momentum distribution is composed of a coherent sum of angular momentum components, each with an amplitude and phase. Here we show, by using photoionization of neon, that a train of attosecond pulses synchronized with an infrared laser field can be used to disentangle these angular momentum components. Two-color, two-photon ionization via a Stark-shifted intermediate state creates an almost pure f-wave with a magnetic quantum number of zero. Interference of the f-wave with a spherically symmetric s-wave provides a holographic reference that enables phase-resolved imaging of the f-wave. I n the Copenhagen interpretation of quantum mechanics, a particle is fully described by its complex wave function Y, which is charac-terized by both an amplitude and phase. How-ever, only the square modulus of the wave function, |Y| 2 , can be directly observed (1, 2). Re-cent developments in attosecond technology based on electron-ion recollision (3) have pro-vided experimental tools for the imaging of the electronic wave function (not its square) in bound states or ionization continua. High-harmonic spec-troscopy on aligned molecules was used to re-construct the highest-occupied molecular orbital of nitrogen (4, 5) and to observe charge migra-tion (6). Strong-field tunneling was used to mea-sure the square modulus of the highest-occupied molecular orbital for selected molecules (7). Fur-thermore, recollision holography (8, 9) permitted a measurement of the phase and amplitude of a continuum electron generated in an intense laser field. Complementary to recollision-based measure-ments, photoelectron spectroscopy with atto-second extreme ultraviolet (XUV) pulses has also measured photoelectron wave packets in continuum states (10--16) by exploiting quantum interferences (17--19). However, decomposition of the wave function of an ejected photoelec-tron into angular momentum eigenstates with a fully characterized amplitude and phase is more difficult. First, in general, a one-photon transition with linearly polarized light gener-ates two orbital angular momentum (') states, according to the selection rule D ' $\sfrac{1}{4}$ T1. Second, because the initial state has a {\dh}2' {\th} 1{\TH}-fold de-generacy (labeled by m, the magnetic quan-tum number) and because m is conserved for interactions with linearly polarized light, photo-electron waves with a range of m are produced. Hence, the photoelectron momentum distribution contains a sum of contributions from different initial states, each of which is a coherent sum of different angular momentum components, making it difficult to decompose the continuum state into individual angular momentum com-ponents (20--22). Here we preferentially create an almost pure f-wave continuum wave function with m = 0 in neon by using an attosecond XUV pulse train synchronized with an infrared (IR) laser pulse through the process of high-harmonic genera-tion. The isolation of the f-wave with m = 0 is attributed to the XUV excitation to a resonant bound state that is Stark-shifted by the IR field.},
  Doi                      = {10.1126/science.aam8393},
  ISSN                     = {0036-8075},
  Timestamp                = {2018.07.12}
}

Electrons detached from atoms or molecules by photoionization carry information about the quantum state from which they originate, as well as the continuum states into which they are released. Generally, the photoelectron momentum distribution is composed of a coherent sum of angular momentum components, each with an amplitude and phase. Here we show, by using photoionization of neon, that a train of attosecond pulses synchronized with an infrared laser field can be used to disentangle these angular momentum components. Two-color, two-photon ionization via a Stark-shifted intermediate state creates an almost pure f-wave with a magnetic quantum number of zero. Interference of the f-wave with a spherically symmetric s-wave provides a holographic reference that enables phase-resolved imaging of the f-wave. I n the Copenhagen interpretation of quantum mechanics, a particle is fully described by its complex wave function Y, which is charac-terized by both an amplitude and phase. How-ever, only the square modulus of the wave function, |Y| 2 , can be directly observed (1, 2). Re-cent developments in attosecond technology based on electron-ion recollision (3) have pro-vided experimental tools for the imaging of the electronic wave function (not its square) in bound states or ionization continua. High-harmonic spec-troscopy on aligned molecules was used to re-construct the highest-occupied molecular orbital of nitrogen (4, 5) and to observe charge migra-tion (6). Strong-field tunneling was used to mea-sure the square modulus of the highest-occupied molecular orbital for selected molecules (7). Fur-thermore, recollision holography (8, 9) permitted a measurement of the phase and amplitude of a continuum electron generated in an intense laser field. Complementary to recollision-based measure-ments, photoelectron spectroscopy with atto-second extreme ultraviolet (XUV) pulses has also measured photoelectron wave packets in continuum states (10–16) by exploiting quantum interferences (17–19). However, decomposition of the wave function of an ejected photoelec-tron into angular momentum eigenstates with a fully characterized amplitude and phase is more difficult. First, in general, a one-photon transition with linearly polarized light gener-ates two orbital angular momentum (') states, according to the selection rule D ' $\sfrac{1}{4}$ T1. Second, because the initial state has a ð2' þ 1Þ-fold de-generacy (labeled by m, the magnetic quan-tum number) and because m is conserved for interactions with linearly polarized light, photo-electron waves with a range of m are produced. Hence, the photoelectron momentum distribution contains a sum of contributions from different initial states, each of which is a coherent sum of different angular momentum components, making it difficult to decompose the continuum state into individual angular momentum com-ponents (20–22). Here we preferentially create an almost pure f-wave continuum wave function with m = 0 in neon by using an attosecond XUV pulse train synchronized with an infrared (IR) laser pulse through the process of high-harmonic genera-tion. The isolation of the f-wave with m = 0 is attributed to the XUV excitation to a resonant bound state that is Stark-shifted by the IR field.

@Article{Wang2017,
  Title                    = {Monitoring non-adiabatic dynamics in CS2 with time- and energy-resolved photoelectron spectra of wavepackets},
  Author                   = {Wang, K. and McKoy, V. and Hockett, P. and Stolow, A. and Schuurman, M.S.},
  Journal                  = {Chemical Physics Letters},
  Year                     = {2017},

  Abstract                 = {We report results from a novel fully ab initio method for simulating the time-resolved photoelectron angular distributions around conical intersections in CS2. The technique employs wavepacket densities obtained with the multiple spawning method in conjunction with geometry- and energy-dependent photoionization matrix elements. The robust agreement of the calculated molecular-frame photoelectron angular distributions with measured values for CS2 demonstrates that this approach can successfully illuminate, and disentangle, the underlying coupled nuclear and electronic dynamics around conical intersections in polyatomic molecules. © 2017 Elsevier B.V.},
  Document_type            = {Article in Press},
  Doi                      = {10.1016/j.cplett.2017.02.014},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013194897&doi=10.1016%2fj.cplett.2017.02.014&partnerID=40&md5=76b56f8a2c14354ae018554315eccbd6}
}

We report results from a novel fully ab initio method for simulating the time-resolved photoelectron angular distributions around conical intersections in CS2. The technique employs wavepacket densities obtained with the multiple spawning method in conjunction with geometry- and energy-dependent photoionization matrix elements. The robust agreement of the calculated molecular-frame photoelectron angular distributions with measured values for CS2 demonstrates that this approach can successfully illuminate, and disentangle, the underlying coupled nuclear and electronic dynamics around conical intersections in polyatomic molecules. © 2017 Elsevier B.V.

@Article{Zarkeshian2017,
  Title                    = {Entanglement between more than two hundred macroscopic atomic ensembles in a solid},
  Author                   = {Zarkeshian, P. and Deshmukh, C. and Sinclair, N. and Goyal, S.K. and Aguilar, G.H. and Lefebvre, P. and Puigibert, M.G. and Verma, V.B. and Marsili, F. and Shaw, M.D. and Nam, S.W. and Heshami, K. and Oblak, D. and Tittel, W. and Simon, C.},
  Journal                  = {Nature Communications},
  Year                     = {2017},
  Number                   = {1},
  Volume                   = {8},

  __markedentry            = {[paul:]},
  Abstract                 = {There are both fundamental and practical motivations for studying whether quantum entanglement can exist in macroscopic systems. However, multiparty entanglement is generally fragile and difficult to quantify. Dicke states are multiparty entangled states where a single excitation is delocalized over many systems. Building on previous work on quantum memories for photons, we create a Dicke state in a solid by storing a single photon in a crystal that contains many large atomic ensembles with distinct resonance frequencies. The photon is re-emitted at a well-defined time due to an interference effect analogous to multi-slit diffraction. We derive a lower bound for the number of entangled ensembles based on the contrast of the interference and the single-photon character of the input, and we experimentally demonstrate entanglement between over two hundred ensembles, each containing a billion atoms. We also illustrate the fact that each individual ensemble contains further entanglement. {\copyright} 2017 The Author(s).},
  Affiliation              = {Institute for Quantum Science and Technology, Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada; National Institute of Standards and Technology, Boulder, CO, United States; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, United States; National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada},
  Art_number               = {906},
  Document_type            = {Article},
  Doi                      = {10.1038/s41467-017-00897-7},
  Source                   = {Scopus},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031702516&doi=10.1038%2fs41467-017-00897-7&partnerID=40&md5=908ab4fd49c99d99065af18814fdb9b6}
}

There are both fundamental and practical motivations for studying whether quantum entanglement can exist in macroscopic systems. However, multiparty entanglement is generally fragile and difficult to quantify. Dicke states are multiparty entangled states where a single excitation is delocalized over many systems. Building on previous work on quantum memories for photons, we create a Dicke state in a solid by storing a single photon in a crystal that contains many large atomic ensembles with distinct resonance frequencies. The photon is re-emitted at a well-defined time due to an interference effect analogous to multi-slit diffraction. We derive a lower bound for the number of entangled ensembles based on the contrast of the interference and the single-photon character of the input, and we experimentally demonstrate entanglement between over two hundred ensembles, each containing a billion atoms. We also illustrate the fact that each individual ensemble contains further entanglement. © 2017 The Author(s).

@Article{Bustard2016,
  Title                    = {Reducing noise in a Raman quantum memory},
  Author                   = {Bustard, P.J. and England, D.G. and Heshami, K. and Kupchak, C. and Sussman, B.J.},
  Journal                  = {Optics Letters},
  Year                     = {2016},
  Number                   = {21},
  Pages                    = {5055-5058},
  Volume                   = {41},
  Abstract                 = {Optical quantum memories are an important component of future optical and hybrid quantum technologies. Raman schemes are strong candidates for use with ultrashort optical pulses due to their broad bandwidth; however, the elimination of deleterious four-wave mixing noise from Raman memories is critical for practical applications. Here, we demonstrate a quantum memory using the rotational states of hydrogen molecules at room temperature. Polarization selection rules prohibit four-wave mixing, allowing the storage and retrieval of attenuated coherent states with a mean photon number 0.9 and a pulse duration 175 fs. The 1/e memory lifetime is 85.5 ps, demonstrating a time-bandwidth product of ≈480 in a memory that is well suited for use with broadband heralded down-conversion and fiber-based photon sources. © 2016 Optical Society of America.},
  Document_type            = {Article},
  Doi                      = {10.1364/OL.41.005055},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995468087&doi=10.1364%2fOL.41.005055&partnerID=40&md5=8c2415100d2621542196e984ff35a4ec}
}

Optical quantum memories are an important component of future optical and hybrid quantum technologies. Raman schemes are strong candidates for use with ultrashort optical pulses due to their broad bandwidth; however, the elimination of deleterious four-wave mixing noise from Raman memories is critical for practical applications. Here, we demonstrate a quantum memory using the rotational states of hydrogen molecules at room temperature. Polarization selection rules prohibit four-wave mixing, allowing the storage and retrieval of attenuated coherent states with a mean photon number 0.9 and a pulse duration 175 fs. The 1/e memory lifetime is 85.5 ps, demonstrating a time-bandwidth product of ≈480 in a memory that is well suited for use with broadband heralded down-conversion and fiber-based photon sources. © 2016 Optical Society of America.

@Article{Bustard2016a,
  Title                    = {Raman-induced slow-light delay of THz-bandwidth pulses},
  Author                   = {Bustard, P.J. and Heshami, K. and England, D.G. and Spanner, M. and Sussman, B.J.},
  Journal                  = {Physical Review A - Atomic, Molecular, and Optical Physics},
  Year                     = {2016},
  Number                   = {4},
  Volume                   = {93},
  Abstract                 = {We propose and experimentally demonstrate a scheme to generate optically controlled delays based on off-resonant Raman absorption. Dispersion in a transparency window between two neighboring, optically activated Raman absorption lines is used to reduce the group velocity of broadband 765 nm pulses. We implement this approach in a potassium titanyl phosphate (KTP) waveguide at room temperature, and demonstrate Raman-induced delays of up to 140 fs for a 650-fs duration, 1.8-THz bandwidth, pulse. Our approach should be applicable to single-photon signals, offers wavelength tunability, and is a step toward processing ultrafast photons. © 2016 American Physical Society.},
  Art_number               = {043810},
  Document_type            = {Article},
  Doi                      = {10.1103/PhysRevA.93.043810},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963657422&doi=10.1103%2fPhysRevA.93.043810&partnerID=40&md5=26332fb545ba4a09044c24be35daf8fc}
}

We propose and experimentally demonstrate a scheme to generate optically controlled delays based on off-resonant Raman absorption. Dispersion in a transparency window between two neighboring, optically activated Raman absorption lines is used to reduce the group velocity of broadband 765 nm pulses. We implement this approach in a potassium titanyl phosphate (KTP) waveguide at room temperature, and demonstrate Raman-induced delays of up to 140 fs for a 650-fs duration, 1.8-THz bandwidth, pulse. Our approach should be applicable to single-photon signals, offers wavelength tunability, and is a step toward processing ultrafast photons. © 2016 American Physical Society.

@Conference{England2016a,
  Title                    = {Applications of a picosecond-lifetime quantum memory},
  Author                   = {England, D.G. and Bustard, P.J. and Sussman, B.J. and Fisher, K.A.G. and Maclean, J.-P.W. and Resch, K.J.},
  Year                     = {2016},
  Abstract                 = {We demonstrate a quantum memory using the optical phonon modes of room-temperature diamond [1, 2]. The memory stores THz-bandwidth single photons produced by parametric down-conversion for several picoseconds and offers operations upon the stored light. © 2016 OSA.},
  Art_number               = {7787652},
  Document_type            = {Conference Paper},
  Journal                  = {2016 Conference on Lasers and Electro-Optics, CLEO 2016},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010638292&partnerID=40&md5=b253d98cf0057a473c074b81c9359f6e}
}

We demonstrate a quantum memory using the optical phonon modes of room-temperature diamond [1, 2]. The memory stores THz-bandwidth single photons produced by parametric down-conversion for several picoseconds and offers operations upon the stored light. © 2016 OSA.

@Article{England2016,
  Title                    = {Phonon-Mediated Nonclassical Interference in Diamond},
  Author                   = {England, D.G. and Fisher, K.A.G. and MacLean, J.-P.W. and Bustard, P.J. and Heshami, K. and Resch, K.J. and Sussman, B.J.},
  Journal                  = {Physical Review Letters},
  Year                     = {2016},
  Number                   = {7},
  Volume                   = {117},
  Abstract                 = {Quantum interference of single photons is a fundamental aspect of many photonic quantum processing and communication protocols. Interference requires that the multiple pathways through an interferometer be temporally indistinguishable to within the coherence time of the photon. In this Letter, we use a diamond quantum memory to demonstrate interference between quantum pathways, initially temporally separated by many multiples of the optical coherence time. The quantum memory can be viewed as a light-matter beam splitter, mapping a THz-bandwidth single photon to a variable superposition of the output optical mode and stored phononic mode. Because the memory acts both as a beam splitter and as a buffer, the relevant coherence time for interference is not that of the photon, but rather that of the memory. We use this mechanism to demonstrate nonclassical single-photon and two-photon interference between quantum pathways initially separated by several picoseconds, even though the duration of the photons themselves is just ∼250 fs. © 2016 American Physical Society.},
  Art_number               = {073603},
  Document_type            = {Article},
  Doi                      = {10.1103/PhysRevLett.117.073603},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982095459&doi=10.1103%2fPhysRevLett.117.073603&partnerID=40&md5=25216c896531ed3faf23fb7fbcaaf41c}
}

Quantum interference of single photons is a fundamental aspect of many photonic quantum processing and communication protocols. Interference requires that the multiple pathways through an interferometer be temporally indistinguishable to within the coherence time of the photon. In this Letter, we use a diamond quantum memory to demonstrate interference between quantum pathways, initially temporally separated by many multiples of the optical coherence time. The quantum memory can be viewed as a light-matter beam splitter, mapping a THz-bandwidth single photon to a variable superposition of the output optical mode and stored phononic mode. Because the memory acts both as a beam splitter and as a buffer, the relevant coherence time for interference is not that of the photon, but rather that of the memory. We use this mechanism to demonstrate nonclassical single-photon and two-photon interference between quantum pathways initially separated by several picoseconds, even though the duration of the photons themselves is just ∼250 fs. © 2016 American Physical Society.

@Article{Fisher2016,
  Title                    = {Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory},
  Author                   = {Fisher, K.A.G. and England, D.G. and MacLean, J.-P.W. and Bustard, P.J. and Resch, K.J. and Sussman, B.J.},
  Journal                  = {Nature Communications},
  Year                     = {2016},
  Volume                   = {7},
  Abstract                 = {The spectral manipulation of photons is essential for linking components in a quantum network. Large frequency shifts are needed for conversion between optical and telecommunication frequencies, while smaller shifts are useful for frequency-multiplexing quantum systems, in the same way that wavelength division multiplexing is used in classical communications. Here we demonstrate frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory. Heralded 723.5 nm photons, with 4.1 nm bandwidth, are stored as optical phonons in the diamond via a Raman transition. Upon retrieval from the diamond memory, the spectral shape of the photons is determined by a tunable read pulse through the reverse Raman transition. We report central frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 and 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, as an integrated platform for photon storage and spectral conversion.},
  Art_number               = {11200},
  Document_type            = {Article},
  Doi                      = {10.1038/ncomms11200},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962682888&doi=10.1038%2fncomms11200&partnerID=40&md5=f93fc97191350eaedccdc73f77a90d27}
}

The spectral manipulation of photons is essential for linking components in a quantum network. Large frequency shifts are needed for conversion between optical and telecommunication frequencies, while smaller shifts are useful for frequency-multiplexing quantum systems, in the same way that wavelength division multiplexing is used in classical communications. Here we demonstrate frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory. Heralded 723.5 nm photons, with 4.1 nm bandwidth, are stored as optical phonons in the diamond via a Raman transition. Upon retrieval from the diamond memory, the spectral shape of the photons is determined by a tunable read pulse through the reverse Raman transition. We report central frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 and 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, as an integrated platform for photon storage and spectral conversion.

@Article{Heshami2016,
  Title                    = {Quantum memories: emerging applications and recent advances},
  Author                   = {Heshami, K. and England, D.G. and Humphreys, P.C. and Bustard, P.J. and Acosta, V.M. and Nunn, J. and Sussman, B.J.},
  Journal                  = {Journal of Modern Optics},
  Year                     = {2016},
  Number                   = {20},
  Pages                    = {2005-2028},
  Volume                   = {63},
  Abstract                 = {Quantum light–matter interfaces are at the heart of photonic quantum technologies. Quantum memories for photons, where non-classical states of photons are mapped onto stationary matter states and preserved for subsequent retrieval, are technical realizations enabled by exquisite control over interactions between light and matter. The ability of quantum memories to synchronize probabilistic events makes them a key component in quantum repeaters and quantum computation based on linear optics. This critical feature has motivated many groups to dedicate theoretical and experimental research to develop quantum memory devices. In recent years, exciting new applications, and more advanced developments of quantum memories, have proliferated. In this review, we outline some of the emerging applications of quantum memories in optical signal processing, quantum computation and non-linear optics. We review recent experimental and theoretical developments, and their impacts on more advanced photonic quantum technologies based on quantum memories. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.},
  Document_type            = {Review},
  Doi                      = {10.1080/09500340.2016.1148212},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961215936&doi=10.1080%2f09500340.2016.1148212&partnerID=40&md5=c31cd86dff39a0b63548b7da7f4d8cfa}
}

Quantum light–matter interfaces are at the heart of photonic quantum technologies. Quantum memories for photons, where non-classical states of photons are mapped onto stationary matter states and preserved for subsequent retrieval, are technical realizations enabled by exquisite control over interactions between light and matter. The ability of quantum memories to synchronize probabilistic events makes them a key component in quantum repeaters and quantum computation based on linear optics. This critical feature has motivated many groups to dedicate theoretical and experimental research to develop quantum memory devices. In recent years, exciting new applications, and more advanced developments of quantum memories, have proliferated. In this review, we outline some of the emerging applications of quantum memories in optical signal processing, quantum computation and non-linear optics. We review recent experimental and theoretical developments, and their impacts on more advanced photonic quantum technologies based on quantum memories. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

@Article{Hockett2016b,
  Title                    = {{ePSproc: Post-processing suite for ePolyScat electron-molecule scattering calculations}},
  Author                   = {Hockett, Paul},
  Journal                  = {Authorea},
  Year                     = {2016},

  __markedentry            = {[paul:]},
  Doi                      = {10.6084/m9.figshare.3545639},
  Timestamp                = {2018.07.12},
  Url                      = {https://www.authorea.com/users/71114/articles/122402/{\_}show{\_}article}
}

@Article{Hockett2016c,
  Title                    = {{Response to 'Comment on "Time delays in molecular photoionization"': Extended Discussion {\&} Technical Notes}},
  Author                   = {Hockett, Paul and Frumker, Eugene},
  Journal                  = {arXiv},
  Year                     = {2016},

  Month                    = dec,
  Volume                   = {1612.00481},

  __markedentry            = {[paul:]},
  Abstract                 = {In a comment on our article Time delays in molecular photoionization [1], Baykusheva {\&} W$\backslash$"orner reproduce canonical scattering theory, and assert that our results are inconsistent with this well-established theory [2]. We absolutely refute this assertion and the spirit of the comment, although we do agree with Baykusheva {\&} W$\backslash$"orner that the textbook theory is correct. In a short response, Response to Comment on "Time delays in molecular photoionization" [3], we have already provided a clear rebuttal of the comment, but gave no technical details. In this fuller response we extend those brief comments in the spirit of completeness and clarity, and provide three clear rebuttals to Baykusheva {\&} W$\backslash$"orner based on (1) logical fallacy (category error), (2) theoretical details of the original article, (3) textural content of the original article. In particular, rebuttal (1) clearly and trivially points to the fact that there is no issue here whatsoever, with recourse to theoretical details barely required to demonstrate this, as outlined in the short version of our response. Our numerical results are correct and reproduce known physical phenomena, as discussed in the original article hence, as careful readers will recognise, the formalism used is canonical scattering theory, and cannot be anything other. In fact, there is no new fundamental physics here to dispute whatsoever, and nor was this the raison d'etre of the original article. Additionally, rebuttal (2) provides the opportunity to discuss, at length, some of these textbook aspects of photoionization theory, and we hope this discussion might be of service to new researchers entering this challenging field.},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1612.00481},
  Eprint                   = {1612.00481},
  Timestamp                = {2018.07.12},
  Url                      = {http://arxiv.org/abs/1612.00481}
}

In a comment on our article Time delays in molecular photoionization [1], Baykusheva & W$\$"orner reproduce canonical scattering theory, and assert that our results are inconsistent with this well-established theory [2]. We absolutely refute this assertion and the spirit of the comment, although we do agree with Baykusheva & W$\$"orner that the textbook theory is correct. In a short response, Response to Comment on "Time delays in molecular photoionization" [3], we have already provided a clear rebuttal of the comment, but gave no technical details. In this fuller response we extend those brief comments in the spirit of completeness and clarity, and provide three clear rebuttals to Baykusheva & W$\$"orner based on (1) logical fallacy (category error), (2) theoretical details of the original article, (3) textural content of the original article. In particular, rebuttal (1) clearly and trivially points to the fact that there is no issue here whatsoever, with recourse to theoretical details barely required to demonstrate this, as outlined in the short version of our response. Our numerical results are correct and reproduce known physical phenomena, as discussed in the original article hence, as careful readers will recognise, the formalism used is canonical scattering theory, and cannot be anything other. In fact, there is no new fundamental physics here to dispute whatsoever, and nor was this the raison d'etre of the original article. Additionally, rebuttal (2) provides the opportunity to discuss, at length, some of these textbook aspects of photoionization theory, and we hope this discussion might be of service to new researchers entering this challenging field.

@Article{Hockett2016,
  Title                    = {Time delay in molecular photoionization},
  Author                   = {Hockett, P. and Frumker, E. and Villeneuve, D.M. and Corkum, P.B.},
  Journal                  = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  Year                     = {2016},
  Number                   = {9},
  Volume                   = {49},

  Abstract                 = {Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, the time-delays expected from molecular ionization present a much richer phenomenon, with a strong spatial dependence due to the anisotropic nature of the molecular scattering potential. We investigate this from a scattering theory perspective, and make use of molecular photoionization calculations to examine this effect in representative homonuclear and hetronuclear diatomic molecules, nitrogen and carbon monoxide. We present energy and angle-resolved maps of the Wigner delay time for single-photon valence ionization, and discuss the possibilities for experimental measurements. © 2016 IOP Publishing Ltd.},
  Art_number               = {095602},
  Document_type            = {Article},
  Doi                      = {10.1088/0953-4075/49/9/095602},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84965050711&doi=10.1088%2f0953-4075%2f49%2f9%2f095602&partnerID=40&md5=d819dc5998c7320934a432c0f35df971}
}

Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, the time-delays expected from molecular ionization present a much richer phenomenon, with a strong spatial dependence due to the anisotropic nature of the molecular scattering potential. We investigate this from a scattering theory perspective, and make use of molecular photoionization calculations to examine this effect in representative homonuclear and hetronuclear diatomic molecules, nitrogen and carbon monoxide. We present energy and angle-resolved maps of the Wigner delay time for single-photon valence ionization, and discuss the possibilities for experimental measurements. © 2016 IOP Publishing Ltd.

@Article{Hockett2016a,
  Title                    = {{Augmented Reality with Hololens: Experiential Architectures Embedded in the Real World}},
  Author                   = {Hockett, Paul and Ingleby, Tim},
  Journal                  = {arXiv},
  Year                     = {2016},

  Month                    = oct,
  Pages                    = {1--10},

  __markedentry            = {[paul:]},
  Abstract                 = {Early hands-on experiences with the Microsoft Hololens augmented/mixed reality device are reported and discussed, with a general aim of exploring basic 3D visualization. A range of usage cases are tested, including data visualization and immersive data spaces, in-situ visualization of 3D models and full scale architectural form visualization. Ultimately, the Hololens is found to provide a remarkable tool for moving from traditional visualization of 3D objects on a 2D screen, to fully experiential 3D visualizations embedded in the real world.},
  Archiveprefix            = {arXiv},
  Arxivid                  = {1610.04281},
  Doi                      = {10.22541/au.148821660.05483993},
  Eprint                   = {1610.04281},
  Timestamp                = {2018.07.12},
  Url                      = {http://arxiv.org/abs/1610.04281}
}

Early hands-on experiences with the Microsoft Hololens augmented/mixed reality device are reported and discussed, with a general aim of exploring basic 3D visualization. A range of usage cases are tested, including data visualization and immersive data spaces, in-situ visualization of 3D models and full scale architectural form visualization. Ultimately, the Hololens is found to provide a remarkable tool for moving from traditional visualization of 3D objects on a 2D screen, to fully experiential 3D visualizations embedded in the real world.

@Article{Sinclair2016,
  Title                    = {Proposal and proof-of-principle demonstration of non-destructive detection of photonic qubits using a Tm:LiNbO3 waveguide},
  Author                   = {Sinclair, N. and Heshami, K. and Deshmukh, C. and Oblak, D. and Simon, C. and Tittel, W.},
  Journal                  = {Nature Communications},
  Year                     = {2016},
  Volume                   = {7},
  Abstract                 = {Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications, such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here, we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in LiNbO 3, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion-doped crystals. © 2016 The Author(s).},
  Art_number               = {13454},
  Document_type            = {Article},
  Doi                      = {10.1038/ncomms13454},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995695227&doi=10.1038%2fncomms13454&partnerID=40&md5=e705ed00c91b2eccf16ade12ee34f977}
}

Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications, such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here, we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in LiNbO 3, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion-doped crystals. © 2016 The Author(s).

@Article{Thekkadath2016,
  Title                    = {Optical quantum memory for ultrafast photons using molecular alignment},
  Author                   = {Thekkadath, G.S. and Heshami, K. and England, D.G. and Bustard, P.J. and Sussman, B.J. and Spanner, M.},
  Journal                  = {Journal of Modern Optics},
  Year                     = {2016},
  Number                   = {20},
  Pages                    = {2093-2100},
  Volume                   = {63},
  Abstract                 = {The absorption of broadband photons in atomic ensembles requires either an effective broadening of the atomic transition linewidth, or an off-resonance Raman interaction. Here, we propose a scheme for a quantum memory capable of storing and retrieving ultrafast photons in an ensemble of two-level atoms using a propagation medium with a time–dependent refractive index generated from aligning an ensemble of gas-phase diatomic molecules. The refractive index dynamics generates an effective longitudinal inhomogeneous broadening of the two-level transition. We numerically demonstrate this scheme for storage and retrieval of a weak pulse as short as 50 fs, with a storage time of up to 20 ps. With additional optical control of the molecular alignment dynamics, the storage time can be extended about one nanosecond leading to time–bandwidth products of order 104. This scheme could in principle be achieved using either a hollow-core fibre or a high-pressure gas cell, in a gaseous host medium comprised of diatomic molecules and a two-level atomic vapour at room temperature. © 2016, Copyright of the Crown in Canada 2016 The National Research Council of Canada.},
  Document_type            = {Article},
  Doi                      = {10.1080/09500340.2016.1181218},
  Source                   = {Scopus},
  Timestamp                = {2017.04.27},
  Url                      = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966709063&doi=10.1080%2f09500340.2016.1181218&partnerID=40&md5=50baa5bfbb52d3e5b542ff413e200f05}
}

The absorption of broadband photons in atomic ensembles requires either an effective broadening of the atomic transition linewidth, or an off-resonance Raman interaction. Here, we propose a scheme for a quantum memory capable of storing and retrieving ultrafast photons in an ensemble of two-level atoms using a propagation medium with a time–dependent refractive index generated from aligning an ensemble of gas-phase diatomic molecules. The refractive index dynamics generates an effective longitudinal inhomogeneous broadening of the two-level transition. We numerically demonstrate this scheme for storage and retrieval of a weak pulse as short as 50 fs, with a storage time of up to 20 ps. With additional optical control of the molecular alignment dynamics, the storage time can be extended about one nanosecond leading to time–bandwidth products of order 104. This scheme could in principle be achieved using either a hollow-core fibre or a high-pressure gas cell, in a gaseous host medium comprised of diatomic molecules and a two-level atomic vapour at room temperature. © 2016, Copyright of the Crown in Canada 2016 The National Research Council of Canada.