Update July 2020: now published as Appl. Phys. Lett. 117, 044001 (2020); https://doi.org/10.1063/5.0012429
[Submitted on 1 May 2020]
Peter Svihra, Yingwen Zhang, Paul Hockett, Steven Ferrante, Benjamin Sussman, Duncan England, Andrei Nomerotski
We describe a simple multivariate technique of likelihood ratios for improved discrimination of signal and background in multi-dimensional quantum target detection. The technique combines two independent variables, time difference and summed energy, of a photon pair from the spontaneous parametric down-conversion source into an optimal discriminant. The discriminant performance was studied in experimental data and in Monte-Carlo modelling with clear improvement shown compared to previous techniques. As novel detectors become available, we expect this type of multivariate analysis to become increasingly important in multi-dimensional quantum optics.
UPDATE May 2020 – now in PRA: Phys. Rev. A 101, 053808 – Published 4 May 2020
Sept. 2019 – New on arXiv
(Submitted on 20 Sep 2019)
Quantum illumination (QI) is a quantum sensing technique, employing the strong correlation between entangled photon pairs, which is capable of significantly improving sensitivity in remote target detection under noisy background conditions when compared to classical sensing schemes. The amount of enhancement is directly proportional to the number of measurable correlated modes between the photon pairs. QI had been demonstrated using degrees of freedoms such as temporal correlations and photon number correlations, but never a combination of two or more such continuous variables. In this work, we utilize both temporal and spectral correlation of entangled photon pairs in QI. We achieved over an order of magnitude reduction to the background noise when compared to utilizing only temporal modes. This work represents an important step in realizing a practical, real-time QI system. The demonstrated technique will also be of importance in many other quantum sensing applications and quantum communications.
Phys. Rev. A 101, 053808 – Published 4 May 2020
Update March 2019 – now in Optics Letters, DOI: 10.1364/OL.44.001427
June 2018 – New on arXiv.
(Submitted on 4 Jun 2018 (v1
), last revised 12 Jun 2018 (this version, v2))
Optically induced ultrafast switching of single photons is demonstrated by rotating the photon polarization via the Kerr effect in a commercially available single mode fiber. A switching efficiency of 97\% is achieved with a ∼1.7\,ps switching time, and signal-to-noise ratio of ∼800. Preservation of the quantum state is confirmed by measuring no significant increase in the second-order autocorrelation function g(2)(0). These values are attained with only nanojoule level pump energies that are produced by a laser oscillator with 80\,MHz repetition rate. The results highlight a simple switching device capable of both high-bandwidth operations and preservation of single-photon properties for applications in photonic quantum processing and ultrafast time-gating or switching.
We investigate the use of correlated photon pair sources for the improved quantum-level detection of a target in the presence of a noise background. Photon pairs are generated by spontaneous four-wave mixing, one photon from each pair (the herald) is measured locally while the other (the signal) is sent to illuminate the target. Following diffuse reflection from the target, the signal photons are detected by a receiver and non-classical timing correlations between the signal and herald are measured in the presence of a configurable background noise source. Quantum correlations from the photon pair source can be used to provide an enhanced signal-to-noise ratio when compared to a classical light source of the same intensity.
Phys. Rev. A 99, 023828 – Published 19 February 2019
arXiv 1811.04113 – Submitted on 9 Nov 2018
New article in Optics Letters.
Jennifer Erskine, Duncan England, Connor Kupchak, and Benjamin Sussman
Optics Letters Vol. 43, Issue 4, pp. 907-910 (2018)
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’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.
Connor Kupchak, Philip J. Bustard, Khabat Heshami, Jennifer Erskine, Michael Spanner, Duncan G. England, and Benjamin J. Sussman
Phys. Rev. A 96, 053812 – Published 6 November 2017
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.
Photoionization is a complex quantum mechanical process, with a range of interfering channels playing a role in even the simplest case. For problems in quantum metrology and sensing, a detailed understanding of the process is desirable for accurate measurements; quantum control is also a possible outcome of such understanding. New research in this area will build on recent cutting-edge work at NRC (see below), which probed the fundamental quantum physics of photoionization in atoms and molecules, and metrology work which demonstrated the retrieval of electron wavefunctions via interferometric time-domain measurements.
Four areas of photoionization interferometry are the target of current research:
- Metrology and control with rotational wavepackets.
- Metrology and control with shaped laser pulses.
- Quantum dynamics probed via photoionization interferometry.
- Fundamental properties of photoion and photoelectron coherence.
Depending on interests and experience, project work will be in one (or more) of these areas.
An introduction to this topic, and recent work, can be found in Paul’s DAMOP 2017 talk Phase-sensitive Photoelectron Metrology (below), and via our blog.
Phase-sensitive Photoelectron Metrology – Dr. P. Hockett, presentation at DAMOP 2017 from femtolab.ca on Vimeo.
Malte C Tichy, Florian Mintert and Andreas Buchleitner
Published 21 September 2011 • 2011 IOP Publishing Ltd
Entanglement is nowadays considered as a key quantity for the understanding of correlations, transport properties and phase transitions in composite quantum systems, and thus receives interest beyond the engineered applications in the focus of quantum information science. We review recent experimental and theoretical progress in the study of quantum correlations under that wider perspective, with an emphasis on rigorous definitions of the entanglement of identical particles, and on entanglement studies in atoms and molecules.
Our recent paper on quantum optical signal processing is now published in Nature Communications:
Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory
Nature Communications 7, 11200, 2016
Kent A.G. Fisher, Duncan G. England, Jean-Philippe W. MacLean, Philip J. Bustard, Kevin J. Resch & Benjamin J. Sussman
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.
April 2016 – Article in Nature Communications
Oct. 2015 – Article on the arxiv