Professor Ian Walmsley CBE FRS FCGI

Abstract:

© 2020, The Author(s). Quantum phenomena such as entanglement can improve fundamental limits on the sensitivity of a measurement probe. In optical interferometry, a probe consisting of N entangled photons provides up to a N enhancement in phase sensitivity compared to a classical probe of the same energy. Here, we employ high-gain parametric down-conversion sources and photon-number-resolving detectors to perform interferometry with heralded quantum probes of sizes up to N = 8 (i.e. measuring up to 16-photon coincidences). Our probes are created by injecting heralded photon-number states into an interferometer, and in principle provide quantum-enhanced phase sensitivity even in the presence of significant optical loss. Our work paves the way toward quantum-enhanced interferometry using large entangled photonic states.

Abstract:

We report the observation of a mode associated with a topological defect in the bulk of a 2D photonic material by introducing a vortex distortion to a hexagonal lattice analogous to graphene. The observed modes lie midgap at zero energy and are closely related to Majorana bound states in superconducting vortices. This is the first experimental demonstration of the Jackiw-Rossi model [R. Jackiw and P. Rossi, Nucl. Phys. B190, 681 (1981)NUPBBO0550-321310.1016/0550-3213(81)90044-4].

Abstract:

Electro-optic modulators within Mach–Zehnder interferometers are a common construction for optical switches in integrated photonics. A challenge faced when operating at high switching speeds is that noise from the electronic drive signals will effect switching performance. Inspired by the Mach–Zehnder lattice switching devices of Van Campenhout et al. [Opt. Express 17(26), 23793 (2009).] and techniques from the field of Nuclear Magnetic Resonance known as composite pulses, we present switches which offer protection against drive-noise in both the on and off state of the switch for both the phase and intensity information encoded in the switched optical mode.