Noise-Robust and Loss-Tolerant Quantum Steering with Qudits

Abstract

A primary requirement for a robust and unconditionally secure quantum network is the establishment of quantum nonlocal correlations over a realistic channel. While loophole-free tests of Bell nonlocality allow for entanglement certification in such a device-independent setting, they are extremely sensitive to loss and noise, which naturally arise in any practical communication scenario. Quantum steering relaxes the strict technological constraints of Bell nonlocality by reframing it in an asymmetric manner, thus providing the basis for one-sided device-independent quantum networks that can operate under realistic conditions. Here we introduce a noise-robust and loss-tolerant test of quantum steering designed for single detector measurements that harnesses the advantages of high-dimensional entanglement. We showcase the improvements over qubit-based systems by experimentally demonstrating detection loophole-free quantum steering in 53 dimensions through simultaneous loss and noise conditions corresponding to 14.2 dB loss equivalent to 79 km of telecommunication fibre, and 36% of white noise. We go on to show how the use of high dimensions counter-intuitively leads to a dramatic reduction in total measurement time, enabling a quantum steering violation almost two orders of magnitude faster obtained by simply doubling the Hilbert space dimension. By surpassing the constraints imposed upon the device-independent distribution of entanglement, our loss-tolerant, noise-robust, and resource-efficient demonstration of quantum steering proves itself a critical ingredient for making device-independent quantum communication over long distances a reality.

Simultaneously sorting overlapping quantum states of light

“…a positive operator-valued measure (POVM) for non- orthogonal, high-dimensional states. High-dimensional quantum states (or qudits) allow for quantum information to be encoded in a d-dimensional space, enabling quantum communication protocols with increased information capacity and robustness to noise [10][11][12][13][14]. While the theoretical foundation for the necessary measurement strategies has already been developed, their experimental realisation has proved to be a significant challenge.…”