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.

Edwin Barnes | LIP6 - Équipe QI

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

Error-correcting entanglement swapping using a practical logical photon encoding