quantum optics

Multivariate Discrimination in Quantum Target Detection

Multivariate Discrimination in Quantum Target Detection

By Paul

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.

arXiv:2005.00612

Multidimensional quantum illumination via direct measurement of spectro-temporal correlations

Multidimensional quantum illumination via direct measurement of spectro-temporal correlations

By Paul

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

Sept. 2019 – New on arXiv

Yingwen Zhang, Duncan England, Andrei Nomerotski, Peter Svihra, Steven Ferrante, Paul Hockett, Benjamin Sussman
(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.

arXiv:1909.09664

Phys. Rev. A 101, 053808 – Published 4 May 2020

DOI: https://doi.org/10.1103/PhysRevA.101.053808

THz-bandwidth all-optical switching of heralded single photons

THz-bandwidth all-optical switching of heralded single photons

By Paul

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

June 2018 – New on arXiv.

THz-bandwidth all-optical switching of heralded single photons

Connor Kupchak, Jennifer Erskine, Duncan G. England, Benjamin J. Sussman
(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.

Fibre VUV generation & applications

Fibre VUV generation & applications

By Paul

Over the last few months (summer 2018) a new project has been shaping up, in collaboration with colleagues from the PCF division (Russell research group) at MPL.  The aim is to develop new ultrafast experiments based on their hollow-core PCFs, which can be used to provide tuneable UV and VUV. This work is part of our larger source development project, and will develop towards applications in photoelectron metrology and quantum optics (amongst others!).

More details to follow, but for now here are a few images of the work in progress…

Quantum-enhanced standoff detection using correlated photon pairs

Quantum-enhanced standoff detection using correlated photon pairs

By Paul

Duncan G. England, Bhashyam Balaji, Benjamin J. Sussman

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

 

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

By Paul

New article in Optics Letters.

Jennifer Erskine, Duncan England, Connor Kupchak, and Benjamin Sussman

Optics Letters Vol. 43, Issue 4, pp. 907-910 (2018)

https://doi.org/10.1364/OL.43.000907

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

By Paul

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.

Reading today…

Reading today…

By Paul

Nonlinear quantum optics mediated by Rydberg interactions

O Firstenberg, C S Adams and S Hofferberth

Published 30 June 2016 • © 2016 IOP Publishing Ltd
Journal of Physics B: Atomic, Molecular and Optical Physics, Volume 49, Number 15
Special Issue on Rydberg Atomic Physics

By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.

DOI: 10.1088/0953-4075/49/15/152003

Fascinating insight into the topic, which utilises the properties of Rydberg matter to enable traditional non-linear optics to cross over to the quantum regime. From the intro:

One remarkable success of advances in ultra-cold Rydberg physics is the realization of a medium with a large optical nonlinearity at the single photon level [1–3]. Highly excited Rydberg atoms bring something new to the history of optics as they enable quantum nonlinear media where photons are strongly interacting!

Recommended.

Reading today…

Reading today…

By Paul

First On-Sky Fringes with an Up-Conversion Interferometer Tested on a Telescope Array

P. Darré, R. Baudoin, J.-T. Gomes, N. J. Scott, L. Delage, L. Grossard, J. Sturmann, C. Farrington, F. Reynaud, and T. A. Ten Brummelaar
Phys. Rev. Lett. 117, 233902 – Published 29 November 2016

10.1103/PhysRevLett.117.233902

The Astronomical Light Optical Hybrid Analysis project investigates the combined use of a telescope array interferometer and nonlinear optics to propose a new generation of instruments dedicated to high-resolution imaging for infrared astronomy. The nonlinear process of optical frequency conversion transfers the astronomical light to a shorter wavelength domain. Here, we report on the first fringes obtained on the sky with the prototype operated at 1.55  μm in the astronomical H band and implemented on the Center for High Angular Resolution Astronomy telescope array. This seminal result allows us to foresee a future extension to the challenging midinfrared spectral domain.

This is quite interesting as an application of photon up-conversion at low-light levels – in this case for interferometric IR telescope arrays.  The demo in the paper doesn’t show any improvement on the existing configuration (i.e. no non-linear optical step), but in principle could: once one factors in not just lossy detection in the IR, but also lossy beam transport (in the conceptually similar VLTI system it’s about 10% efficient).

The header image shows fig. 1 from the paper.