Gaël Massé - Realistic Bell tests with homodyne measurements

Realistic Bell tests with homodyne measurements

This seminar, given by Gaël Massé, will happend on 10 April 2024, at 9:0. It will take place in Room Not specified.

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Abstract

Bell non-locality has now emerged as the core resource for quantum information processing in a device-independent (DI) manner, i.e. without making assumptions about the underlying quantum model. Notably, it can provide device-independent security proofs for quantum key distribution. We analyze Bell inequalities violations in photonic experiments for which the measurement apparatuses are restricted to homodyne measurements. Through numerical optimization of the Clauser-Horne-Shimony-Holt inequality over homodyne measurements and binning choices, we demonstrate large violations for states with a bounded number of photons. When considering states defined within qubit local subspaces of two Fock states, such as NOON states, a violation is observed solely within the qubit Fock space spanned by zero and two photons. For states living in larger qudit Fock spaces, large violations are obtained. Significant violations are observed even for states containing three photons locally and under realistic values of noise and losses. We propose concrete implementations to achieve such violations based solely upon Gaussian processes and heralding operations. This open new avenues for Bell experiments with homodyne detectors.