Multivariate Discrimination in Quantum Target Detection

Multivariate Discrimination in Quantum Target Detection

Update July 2020: now published as Appl. Phys. Lett. 117, 044001 (2020);

[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.


Multidimensional quantum illumination via direct measurement of spectro-temporal correlations

Multidimensional quantum illumination via direct measurement of spectro-temporal correlations

UPDATE May 2020 – now in PRA: Phys. Rev. A 101, 053808 – Published 4 May 2020

Sept. 2019 – New on arXiv

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


THz-bandwidth all-optical switching of heralded single photons

THz-bandwidth all-optical switching of heralded single photons

Update March 2019 – now in Optics Letters, DOI: 10.1364/OL.44.001427

June 2018 – New on arXiv.

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.

Quantum-enhanced standoff detection using correlated photon pairs

Quantum-enhanced standoff detection using correlated photon pairs

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


Quantum Canada

Quantum Canada

Feb 2019: New article in Quantum Science and Technology

Canada ranks among the world’s leading nations in quantum research, building on investments of more than $1 billion in the past decade alone. Canada’s amassed research expertise, growing private-sector impact, and government commitments to innovation and competitiveness, place the country in a strong position, as scientific advances drive quantum technology development. Here, we summarize the steps Canada has taken to build quantum research excellence and to support a growing quantum industrial base. We also discuss Canadian quantum community efforts to solidify and build the nation’s leadership, as the technology revolution unfolds.

Ben SussmanPaul CorkumAlexandre BlaisDavid Cory and Andrea Damascelli

2019 Quantum Sci. Technol. 4 020503

DOI: 10.1088/2058-9565/ab029d

Reading today…

Reading today…

Remote quantum entanglement between two micromechanical oscillators

Ralf RiedingerAndreas WallucksIgor MarinkovićClemens LöschnauerMarkus AspelmeyerSungkun Hong & Simon Gröblacher

Nature volume 556pages 473–477 (2018)

Entanglement, an essential feature of quantum theory that allows for inseparable quantum correlations to be shared between distant parties, is a crucial resource for quantum networks1. Of particular importance is the ability to distribute entanglement between remote objects that can also serve as quantum memories. This has been previously realized using systems such as warm2,3 and cold atomic vapours4,5, individual atoms6 and ions7,8, and defects in solid-state systems9,10,11. Practical communication applications require a combination of several advantageous features, such as a particular operating wavelength, high bandwidth and long memory lifetimes. Here we introduce a purely micromachined solid-state platform in the form of chip-based optomechanical resonators made of nanostructured silicon beams. We create and demonstrate entanglement between two micromechanical oscillators across two chips that are separated by 20 centimetres . The entangled quantum state is distributed by an optical field at a designed wavelength near 1,550 nanometres. Therefore, our system can be directly incorporated in a realistic fibre-optic quantum network operating in the conventional optical telecommunication band. Our results are an important step towards the development of large-area quantum networks based on silicon photonics.

(Image above from the related Science news item, Einstein’s ‘spooky action at a distance’ spotted in objects almost big enough to see.)

Reading today…

Reading today…

Building one molecule from a reservoir of two atoms

L. R. Liu, J. D. Hood, Y. Yu, J. T. Zhang, N. R. Hutzler, T. Rosenband, K.-K. Ni

Science 12 Apr 2018: eaar7797, DOI: 10.1126/science.aar7797

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combine exactly two atoms into a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms (one sodium and one cesium) in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photo-association forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits.

Quantum Metrology with Photoelectrons (book)

Quantum Metrology with Photoelectrons (book)

Update April 2018 – the books are now available via IOP, see details at end of post.

Book for IOP Concise Physics series, due early 2018

Dr. Paul Hockett

National Research Council of Canada

Online resources

OSF project (ID: q2v3g) with interactive content and additional resources, DOI: 10.17605/OSF.IO/Q2V3G website, posts tagged “metrology-book” website, posts tagged “video”


Photoionization is an interferometric process, in which multiple paths can contribute to the final continuum photoelectron wavefunction. At the simplest level, interferences between different final angular momentum states are manifest in the energy and angle resolved photoelectron spectra: metrology schemes making use of these interferograms are thus phase-sensitive, and provide a powerful route to detailed understanding of photoionization. In these cases, the continuum wavefunction (and underlying scattering dynamics) can be characterised. At a more complex level, such measurements can also provide a powerful probe for other processes of interest, leading to a more general class of quantum metrology built on phase-sensitive photoelectron imaging.  Since the turn of the century, the increasing availability of photoelectron imaging experiments, along with the increasing sophistication of experimental techniques, and the availability of computational resources for analysis and numerics, has allowed for significant developments in such photoelectron metrology.

Volume I covers the core physics of photoionization, including a range of computational examples. The material is presented as both reference and tutorial, and should appeal to readers of all levels.  Volume II explores applications, and the development of quantum metrology schemes based on photoelectron measurements. The material is more technical, and will appeal more to the specialist reader.

Full text

Quantum Metrology with Photoelectrons

Volume 1
ISBN 978-1-6817-4684-5
Volume 2
ISBN 978-1-6817-4688-3


Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed

Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed

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.


Time-bin-to-polarization conversion of ultrafast photonic qubits

Time-bin-to-polarization conversion of ultrafast photonic qubits

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.