@article{TEXTUAL,
      recid = {11509},
      author = {Hann, Connor T. and Lee, Gideon and Girvin, S. M. and  Jiang, Liang},
      title = {Resilience of Quantum Random Access Memory to Generic  Noise},
      journal = {PRX Quantum},
      address = {2021-04-29},
      number = {TEXTUAL},
      abstract = {<p>Quantum random access memory (QRAM)—memory which  stores classical data but allows queries to be performed in  superposition—is required for the implementation of  numerous quantum algorithms. While naive implementations of  QRAM are highly susceptible to decoherence and hence not  scalable, it has been argued that the bucket-brigade QRAM  architecture  [Giovannetti <em>et al</em>., <a  href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.160501">Phys.  Rev. Lett. 100, 160501 (2008)</a>] is highly resilient to  noise, with the infidelity of a query scaling only  logarithmically with the memory size. In prior analyses,  however, this favorable scaling followed directly from the  use of contrived noise models, thus leaving open the  question of whether experimental implementations would  actually enjoy the purported scaling advantage. In this  work, we study the effects of decoherence on QRAM in full  generality. Our main result is a proof that this favorable  infidelity scaling holds  for <em>arbitrary</em> error channels (including,  e.g., depolarizing noise and coherent errors). Our proof  identifies the origin of this noise resilience as the  limited entanglement among the memory’s components,  and it also reveals that significant architectural  simplifications can be made while preserving the noise  resilience. We verify these results numerically using a  novel classical algorithm for the efficient simulation of  noisy QRAM circuits. Our findings indicate that QRAM can be  implemented with existing hardware in realistically noisy  devices, and that high-fidelity queries are possible  without quantum error correction. Furthermore, we also  prove that the benefits of the bucket-brigade architecture  persist when quantum error correction is used, in which  case the scheme offers improved hardware efficiency and  resilience to logical errors.</p>},
      url = {http://knowledge.uchicago.edu/record/11509},
}