There have been several versions of optical wavelength astronomical imaging interferometers over the years, with the preferred form being Michelson direct detection (though Hanbury-Brown-Twiss is currently in revival). Even though it is prevalent in radio astronomy, using a common reference (e.g., a laser) is known to have a poor signal-to-noise ratio at visible wavelengths as the shot noise introduced by the reference overwhelms the considerably weaker signal collected by the telescopes. In 2012, a team of quantum physicists (Gottesman, Jennewein and Croke (GJC)) proposed a novel method for using a common optical reference that would abate the shot-noise issue: a path-entangled single-photon reference (i.e., a single photon that is split on a beam splitter). Transported to the various telescopes using a quantum network to overcome loss, the distributed single photon is then interfered with the optical field collected by the telescopes. Previously, we successfully demonstrated a proof-of-principle table-top experiment that implements the GJC protocol where we recovered the spatial autocorrelation of quasi-thermal double-slit sources in a single spectral-temporal mode where the single photon was produced by heralded parametric down conversion. Using quantum optics theory, we modeled our system and found good agreement allowing us to extend our model, and compare and contrast with similarly weak, non-single-photon reference sources (e.g., coherent states). Using the knowledge gained from this experiment, we document the plausibility of an on-sky measurement of the sun utilizing a similar phase reference.
Superconducting Nanowire-Single Photon Detectors (SNSPDs) have emerged as the highest-performing single-photon detectors, with detection efficiencies reaching 98%, maximum count rates over 1 Gcount/s, and the ability to distinguish between single-photon and multi-photon events. SNSPDs have enabled our group to demonstrate loophole-free tests of Bell’s inequality and device-independent randomness expansion. In this talk I will discuss a new scheme using SNSPDs for high-rate, high-fidelity entanglement distribution between remote nodes of a quantum network. The scheme uses a high-quality heralded entangled source and all-optical quantum repeaters. I will discuss requirements for the SNSPDs and strategies for achieving interferometric stability across the network. Both will be crucial for achieving high-fidelity entanglement distribution at high rates.
Very-long baseline interferometry has been one of the major astronomical imaging techniques used in the last century for tasks ranging from measuring diameters of stars to imaging black holes at the center of galaxies. However, the usual heterodyne technique is typically limited to radio wavelengths for the longest baselines due to fundamental noise from the local oscillator, which is used to measure the collected electric field in time at each aperture. Further, the visible and near-infrared (V-NIR) wavelengths do not easily allow such measurements due to their higher frequency; so, for optimal performance, the collected fields must be directly interfered with each other to measure the spatial correlation of the stellar light between each aperture. This implies, at V-NIR wavelengths, a practical limitation on the distance between the receivers and the brightness of stellar sources since bringing the fields together is lossy. Several theoretical proposals have promised reduction of this loss by using single photons along with quantum networks and/or quantum memories. We demonstrate a proof-of-principle, table-top experiment of one proposal by interfering path-entangled single photons generated from parametric down conversion and the light collected from a quasi-thermal source occupying a single spectral-temporal mode representing light from a star. The interference signal was then used to recover the spatial autocorrelation of two source distributions: 1 and 2 mm separated double slits. We compare this to a theoretical model and see good agreement. This model allows further comparison to other weak, non-single-photon, local-oscillator sources such as coherent states.
Spectral interferometry is employed to characterize a temporal-mode sorter, also known as a quantum pulse gate, which is essential to ensure efficient information encoding and processing. We present and test a model to reconstruct transfer functions and propose a feasible experiment.
Recent proposals suggest that distributed single photons serving as a ‘non-local oscillator’ can outperform coherent states as a phase reference for long-baseline interferometric imaging of weak sources [1,2]. Such nonlocal quantum states distributed between telescopes can, in-principle, surpass the limitations of conventional interferometric-based astronomical imaging approaches for very-long baselines such as: signal-to-noise, shot noise, signal loss, and faintness of the imaged objects. Here we demonstrate in a table-top experiment, interference between a nonlocal oscillator generated by equal-path splitting of an idler photon from a pulsed, separable, parametric down conversion process and a spectrally single-mode, quasi-thermal source. We compare the single-photon nonlocal oscillator to a more conventional local oscillator with uncertain photon number. Both methods enabled reconstruction of the source’s Gaussian spatial distribution by measurement of the interference visibility as a function of baseline separation and then applying the van Cittert-Zernike theorem [3,4]. In both cases, good qualitative agreement was found with the reconstructed source width and the known source width as measured using a camera. We also report an increase of signal-to-noise per ‘faux’ stellar photon detected when heralding the idler photon. 1593 heralded (non-local oscillator) detection events led to a maximum visibility of ~17% compared to the 10412 unheralded (classical local oscillator) detection events, which gave rise to a maximum visibility of ~10% – the first instance of quantum-enhanced sensing in this context.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.