Entangling Quantum Memories at Channel Capacity
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866914116703092736 |
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| author | Dhara, Prajit Jiang, Liang Guha, Saikat |
| author_facet | Dhara, Prajit Jiang, Liang Guha, Saikat |
| contents | Entangling quantum memories, mediated by optical-frequency or microwave channels, at high rates and fidelities is key for linking qubits across short and long ranges. All well-known protocols encode up to one qubit per optical mode, hence entangling one pair of memory qubits per transmitted mode over the channel, with probability $η$, the channel's transmissivity. The rate is proportional to $η$ ideal Bell states (ebits) per mode. The quantum capacity, $C(η) = -\log_2(1-η)$ ebits per mode, which $\approx 1.44η$ for high loss, i.e., $η\ll 1$, thereby making these schemes near rate-optimal. However, $C(η) \to \infty$ as $η\to 1$, making the known schemes highly rate-suboptimal for shorter ranges. We show that 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 analog information, enables entangling memories at capacity-approaching rates at low loss. We benefit from loss resilience of GKP qudits, and their ability to encode multiple qubits in one mode. Our memory-photon interface further supports the preparation of needed ancilla GKP qudits. We expect our result to spur research in low-loss high-cooperativity cavity-coupled qubits with high-efficiency optical coupling, and demonstrations of high-rate short-range quantum links. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_04272 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Entangling Quantum Memories at Channel Capacity Dhara, Prajit Jiang, Liang Guha, Saikat Quantum Physics Entangling quantum memories, mediated by optical-frequency or microwave channels, at high rates and fidelities is key for linking qubits across short and long ranges. All well-known protocols encode up to one qubit per optical mode, hence entangling one pair of memory qubits per transmitted mode over the channel, with probability $η$, the channel's transmissivity. The rate is proportional to $η$ ideal Bell states (ebits) per mode. The quantum capacity, $C(η) = -\log_2(1-η)$ ebits per mode, which $\approx 1.44η$ for high loss, i.e., $η\ll 1$, thereby making these schemes near rate-optimal. However, $C(η) \to \infty$ as $η\to 1$, making the known schemes highly rate-suboptimal for shorter ranges. We show that 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 analog information, enables entangling memories at capacity-approaching rates at low loss. We benefit from loss resilience of GKP qudits, and their ability to encode multiple qubits in one mode. Our memory-photon interface further supports the preparation of needed ancilla GKP qudits. We expect our result to spur research in low-loss high-cooperativity cavity-coupled qubits with high-efficiency optical coupling, and demonstrations of high-rate short-range quantum links. |
| title | Entangling Quantum Memories at Channel Capacity |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2406.04272 |