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SUMMARY:Time-Efficient Constant-Space-Overhead Fault-Tolerant Quantum Comp
 utation - Hayata Yamasaki\, University of Tokyo
DTSTART:20230928T131500Z
DTEND:20230928T143000Z
UID:TALK204382@talks.cam.ac.uk
CONTACT:Subhayan Roy Moulik
DESCRIPTION:Scalable realization of quantum computing to attain substantia
 l speedups over classical computing requires fault tolerance. Conventional
 ly\, protocols for fault-tolerant quantum computation (FTQC) demand excess
 ive space overhead of physical qubits per logical qubit. A more recent pro
 tocol to achieve constant-space-overhead FTQC using quantum low-density pa
 rity-check (LDPC) codes thus attracts considerable attention but suffers f
 rom another drawback: it incurs polynomially long time overhead. To addres
 s these problems\, we here introduce an alternative approach using a conca
 tenation of multiple small-size quantum codes for the constant-space-overh
 ead FTQC rather than a single large-size quantum LDPC code. We develop tec
 hniques for concatenating different quantum Hamming codes with growing siz
 es. As a result\, we construct a low-overhead protocol to achieve constant
  space overhead and only quasi-polylogarithmic time overhead simultaneousl
 y. Our protocol accomplishes FTQC even if a decoder has non-constant runti
 me\, unlike the existing constant-space-overhead protocol. These results e
 stablish a foundation for FTQC realizing a large class of quantum speedups
  within feasibly bounded space overhead yet negligibly short time overhead
 . This achievement opens a promising avenue for the low-overhead FTQC base
 d on code concatenation.\n\nThe talk is based on the following paper.\n\nh
 ttps://arxiv.org/abs/2207.08826
LOCATION:MR9 (Ground Floor Pavillion B)
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