55th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Monday–Friday, June 3–7, 2024;
Fort Worth, Texas
Session Y10: Quantum Networks
10:30 AM–12:30 PM,
Friday, June 7, 2024
Room: 204AB
Chair: Alberto Marino, Oak Ridge National Laboratory
Abstract: Y10.00002 : Entangling quantum memories at channel capacity
11:00 AM–11:30 AM
Abstract
Presenter:
Saikat Guha
(University of Arizona)
Author:
Saikat Guha
(University of Arizona)
Generating entanglement between quantum memories, mediated by optical-frequency or microwave channels, at high rates and fidelities is key for linking qubits over short to long ranges. In this talk, I will discuss a few architectural alternatives for how to generate heralded entanglement among two quantum memory registers, and their use in repeater and satellite-assisted quantum links. We will discuss some well-known protocols---of both the midpoint-swap and midpoint-source flavors---which encode up to one qubit per optical mode, hence entangling one pair of memory qubits per transmitted mode over the channel, with probability equaling the channel's transmissivity. The rate, measured in ideal Bell states (or, ebits) per mode, is thus proportional to this transmissivity, which is the optimal scaling, in terms of the quantum capacity, at high loss. However, the quantum channel capacity shoots up toward infinity for low loss of the channel connecting the memory registers, making the known schemes highly rate-suboptimal for shorter ranges, viz., intra-processor, data center and even local-area quantum network links. I will discuss how a cavity-assisted memory-photon interface can be used to entangle matter memories with Gottesman-Kitaev-Preskill (GKP) photonic qudits, which along with dual-homodyne entanglement swaps that retain and process the analog information, enables capacity-approaching entanglement rates at low loss. This scheme benefits from the loss resilience of GKP qudits, and their ability to encode multiple qubits in one bosonic mode. Further, the memory-photon interface supports the preparation of needed ancilla GKP qudits. I will end the talk with an overview of research being performed as part of the NSF-funded Center for Quantum Networks, a consortium of multiple universities and companies in the US, working on the full stack development of fault-tolerant quantum networking.