A distillation-teleportation protocol for fault-tolerant QRAM

• URL: http://arxiv.org/abs/2505.20265v1
• Date: Mon, 26 May 2025 17:42:56 GMT
• Title: A distillation-teleportation protocol for fault-tolerant QRAM
• Authors: Alexander M. Dalzell, András Gilyén, Connor T. Hann, Sam McArdle, Grant Salton, Quynh T. Nguyen, Aleksander Kubica, Fernando G. S. L. Brandão,
• Abstract summary: We present a protocol for fault-tolerantly implementing the logical quantum random access memory (QRAM) operation.<n>For coherently accessing classical memories of size $2n$, our protocol consumes only $mathrmpoly(n)$ fault-tolerant quantum resources.
• Score: 95.99192129224721
• License: http://creativecommons.org/licenses/by-sa/4.0/
• Abstract: We present a protocol for fault-tolerantly implementing the logical quantum random access memory (QRAM) operation, given access to a specialized, noisy QRAM device. For coherently accessing classical memories of size $2^n$, our protocol consumes only $\mathrm{poly}(n)$ fault-tolerant quantum resources (logical gates, logical qubits, quantum error correction cycles, etc.), avoiding the need to perform active error correction on all $\Omega(2^n)$ components of the QRAM device. This is the first rigorous conceptual demonstration that a specialized, noisy QRAM device could be useful for implementing a fault-tolerant quantum algorithm. In fact, the fidelity of the device can be as low as $1/\mathrm{poly}(n)$. The protocol queries the noisy QRAM device $\mathrm{poly}(n)$ times to prepare a sequence of $n$-qubit QRAM resource states, which are moved to a general-purpose $\mathrm{poly}(n)$-size processor to be encoded into a QEC code, distilled, and fault-tolerantly teleported into the computation. To aid this protocol, we develop a new gate-efficient streaming version of quantum purity amplification that matches the optimal sample complexity in a wide range of parameters and is therefore of independent interest. The exponential reduction in fault-tolerant quantum resources comes at the expense of an exponential quantity of purely classical complexity: each of the $n$ iterations of the protocol requires adaptively updating the $2^n$-size classical dataset and providing the noisy QRAM device with access to the updated dataset at the next iteration. While our protocol demonstrates that QRAM is more compatible with fault-tolerant quantum computation than previously thought, the need for significant classical computational complexity exposes potentially fundamental limitations to realizing a truly $\mathrm{poly}(n)$-cost fault-tolerant QRAM.

Related papers

• Heterogeneously error-corrected QRAMs [0.8057006406834466]
  We propose a surface code error-corrected QRAM made of heterogeneous code distance logical qubits.<n>Our designs can achieve up to polylogarithmic reduction in query infidelity, producing constant query infidelity scaling.
  arXiv  Detail & Related papers  (2025-04-30T14:23:42Z)
• The Power of Unentangled Quantum Proofs with Non-negative Amplitudes [55.90795112399611]
  We study the power of unentangled quantum proofs with non-negative amplitudes, a class which we denote $textQMA+(2)$. In particular, we design global protocols for small set expansion, unique games, and PCP verification. We show that QMA(2) is equal to $textQMA+(2)$ provided the gap of the latter is a sufficiently large constant.
  arXiv  Detail & Related papers  (2024-02-29T01:35:46Z)
• Systems Architecture for Quantum Random Access Memory [0.6386668251980657]
  Quantum random access memory (QRAM) is a promising architecture for realizing quantum queries. We show how to leverage the intrinsic biased-noise resilience of the proposed QRAM for implementation on either Noisy Intermediate-Scale Quantum (NISQ) or Fault-Tolerant Quantum Computing (FTQC) hardware.
  arXiv  Detail & Related papers  (2023-06-05T20:52:28Z)
• QRAM: A Survey and Critique [1.52292571922932]
  Quantum random-access memory (QRAM) is a mechanism to access data based on addresses which are themselves a quantum state. We use two primary categories of QRAM from the literature: active and passive. In summary, we conclude that cheap, scalableally passive QRAM is unlikely with existing proposals.
  arXiv  Detail & Related papers  (2023-05-17T15:48:48Z)
• Efficient and Error-Resilient Data Access Protocols for a Limited-Sized Quantum Random Access Memory [7.304498344470287]
  We focus on the access of larger data sizes without keeping on increasing the size of the QRAM. We propose a novel protocol for loading data with larger word lengths $k$ without increasing the number of QRAM levels $n$. By exploiting the parallelism in the data query process, our protocol achieves a time complexity of $O(n+k)$ and improves error scaling performance.
  arXiv  Detail & Related papers  (2023-03-09T12:21:18Z)
• Universal qudit gate synthesis for transmons [44.22241766275732]
  We design a superconducting qudit-based quantum processor. We propose a universal gate set featuring a two-qudit cross-resonance entangling gate. We numerically demonstrate the synthesis of $rm SU(16)$ gates for noisy quantum hardware.
  arXiv  Detail & Related papers  (2022-12-08T18:59:53Z)
• Realization of arbitrary doubly-controlled quantum phase gates [62.997667081978825]
  We introduce a high-fidelity gate set inspired by a proposal for near-term quantum advantage in optimization problems. By orchestrating coherent, multi-level control over three transmon qutrits, we synthesize a family of deterministic, continuous-angle quantum phase gates acting in the natural three-qubit computational basis.
  arXiv  Detail & Related papers  (2021-08-03T17:49:09Z)
• Fault-tolerant Coding for Quantum Communication [71.206200318454]
  encode and decode circuits to reliably send messages over many uses of a noisy channel. For every quantum channel $T$ and every $eps>0$ there exists a threshold $p(epsilon,T)$ for the gate error probability below which rates larger than $C-epsilon$ are fault-tolerantly achievable. Our results are relevant in communication over large distances, and also on-chip, where distant parts of a quantum computer might need to communicate under higher levels of noise.
  arXiv  Detail & Related papers  (2020-09-15T15:10:50Z)
• Succinct Blind Quantum Computation Using a Random Oracle [0.8702432681310399]
  We give a new universal blind quantum computation protocol. The protocol's first phase is succinct, that is, its complexity is independent of circuit size.
  arXiv  Detail & Related papers  (2020-04-27T07:47:11Z)
• Quantum Gram-Schmidt Processes and Their Application to Efficient State Read-out for Quantum Algorithms [87.04438831673063]
  We present an efficient read-out protocol that yields the classical vector form of the generated state. Our protocol suits the case that the output state lies in the row space of the input matrix. One of our technical tools is an efficient quantum algorithm for performing the Gram-Schmidt orthonormal procedure.
  arXiv  Detail & Related papers  (2020-04-14T11:05:26Z)
• Parallelising the Queries in Bucket Brigade Quantum RAM [69.43216268165402]
  Quantum algorithms often use quantum RAMs (QRAM) for accessing information stored in a database-like manner. We show a systematic method to significantly reduce the effective query time by using Clifford+T gate parallelism. We conclude that, in theory, fault-tolerant bucket brigade quantum RAM queries can be performed approximately with the speed of classical RAM.
  arXiv  Detail & Related papers  (2020-02-21T14:50:03Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.