Paul Hilaire | LIP6 - Équipe QI

A Spin-Optical Quantum Computing Architecture

Thu, 09 Nov 2023 00:00:00 +0000

We introduce an adaptable and modular hybrid architecture designed for fault-tolerant quantum computing. It combines quantum emitters and linear-optical entangling gates to leverage the strength of both matter-based and photonic-based approaches. A key feature of the architecture is its practicality, grounded in the utilisation of experimentally proven optical components. Our framework enables the execution of any quantum error correcting code, but in particular maintains scalability for low-density parity check codes by exploiting built-in non-local connectivity through distant optical links. To gauge its efficiency, we evaluated the architecture using a physically motivated error model. It exhibits loss tolerance comparable to existing all-photonic architecture but without the need for intricate linear-optical resource-state-generation modules that conventionally rely on resource-intensive multiplexing. The versatility of the architecture also offers uncharted avenues for further advancing performance standards.

Linear optical logical Bell state measurements with optimal loss-tolerance threshold

Mon, 06 Nov 2023 00:00:00 +0000

Quantum threshold theorems impose hard limits on the hardware capabilities to process quantum information. We derive tight and fundamental upper bounds to loss-tolerance thresholds in different linear-optical quantum information processing settings through an adversarial framework, taking into account the intrinsically probabilistic nature of linear optical Bell measurements. For logical Bell state measurements - ubiquitous operations in photonic quantum information - we demonstrate analytically that linear optics can achieve the fundamental loss threshold imposed by the no-cloning theorem even though, following the work of Lee et al., (Phys. Rev. A 100, 052303 (2019)), the constraint was widely assumed to be stricter. We spotlight the assumptions of the latter publication and find their bound holds for a logical Bell measurement built from adaptive physical linear-optical Bell measurements. We also give an explicit even stricter bound for non-adaptive Bell measurements.

Error-correcting entanglement swapping using a practical logical photon encoding

Mon, 01 Nov 2021 00:00:00 +0000

The implementation of a quantum internet requires the distribution of entanglement over long distances, which is facilitated by entanglement swapping using photonic Bell state measurements (BSMs). Yet, two-photon Bell state measurement schemes have in general a success probability of at best 50%. Here, we propose to overcome this limitation by logically encoding photonic qubits onto photonic tree graph states, an error-correcting code that can be deterministically generated with few matter qubits. We show that we can perform a near-deterministic logical BSM even in the presence of photon losses through two measurement schemes that either use static linear optics or require feed-forward. In addition, we show that these two schemes are also resistant to errors.