Large-scale quantum photonics requires the integration of several elements on the same chip, including quantum emitters and memories, active photonics, and single-photon detectors. In this talk, I will report on i) our recent work integrating superconducting nanowire single-photon detectors (SNSPD) with mechanically reconfigurable integrated photonics, and ii) our recently developed method for integration of SNSPDs onto arbitrary photonic substrates.
Thin Film Lithium Niobate (TFLN) photonic integrated circuits offer several improvements over other platforms in terms of material loss, energy efficiency, and operational bandwidth. We review our recent demonstration of quadrature phase shift keying in an ultrasmall TFLN photonic crystal-based IQ modulator. Our modulator features a footprint of 40 × 200 μm2 along with quality factors approaching 105 providing it with a Vπ = 1.16 V [H. Larocque et al. CLEO 2023, paper STh1R.3; H. Larocque et al. arXiv:2312.16746]. We discuss an extension to and optimization of quadrature amplitude modulation encoding schemes tailored to the device’s voltage response, including the use of a deep neural network for streamlining bit error rate minimization.
In recent years, the on-demand generation of structured polychromatic fields has introduced the possibility of creating more complicated polarization states. However, the study of the curves traced by the polychromatic electric field has been limited to the paraxial case, leading to Lissajous-like curves. In contrast, the new zoo of the 3-dimensional polarization curves remain almost unexplored. In this work, we propose the analysis of the 3-dimensional polarization curves generated by non-paraxial polychromatic beams. The non-paraxial regime is achieved through vector diffraction by an aplanatic lens.
Quantum walks serve as novel tools for performing efficient quantum computation and simulation. In a recent experimental demonstration [1] we have realized photonic quantum walks for simulating cyclic quantum systems, such as hexagonal lattices or aromatic molecules like benzene. In that experiment we explored the wave function dynamics and the probability distribution of a quantum particle located on a six-site system (with periodic boundary conditions), alongside with simpler demonstration of three- and four-site systems, under various initial conditions. Localization and revival of the wave function were demonstrated. After revisiting that experiment we will theoretically analyze the case of noisy quantum walks by implementing the bit-phase flip channel. This will allow us to draw conclusions regarding the performance of our photonic quantum simulation in noisy environments. Finally, we will briefly outline some future directions.
Quantum imaging attempts to exploit the quantum features of light in order to enhance one or more aspects of classical imaging. Here we focus on two quantum imaging schemes – ghost imaging and interaction-free imaging – and moreover, on their combination. After a brief overview of the subject we report the main result: a laboratory demonstration of a new imaging scheme termed Interaction-Free Ghost Imaging. We then explain its merits for the task of imaging various structured objects. Next, we discuss an outgrowth of this scheme used for the purpose of nonlocal quantum erasure. We conclude by mentioning some related, low-dose schemes (both quantum and quantum-inspired) for X-ray and gammaray sources.
Correlated light (either classical or quantum) can be employed in various ways to improve resolution and measurement sensitivity. In an “interaction-free” measurement, a single photon can be used to reveal the presence of an object placed within one arm of an interferometer without being absorbed by it. This method has previously been applied to imaging. With a technique known as “ghost imaging”, entangled photon pairs are used for detecting an opaque object with significantly improved signal-to-noise ratio while preventing over-illumination. Here, we integrate these two methods to obtain a new imaging technique which we term “interaction-free ghost-imaging” that possesses the benefits of both techniques. While improving the image quality of conventional ghost-imaging, this new technique is also sensitive to phase and polarization changes in the photons introduced by a structured object. Furthermore, thanks to the “interaction-free” nature of this new technique, it is possible to reduce the number of photons required to produce a clear image of the object (which could be otherwise damaged by the photons) making this technique superior for probing light-sensitive materials and eventually biological tissues. If time allows, I will discuss some follow-up works involving partial measurements and remote erasure/completion of images. The latter techniques can help to suppress various types of noise during the imaging process.
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