Flag Gadgets Based on Classical Codes

Fault-tolerant syndrome extraction is a key ingredient in implementing fault-tolerant quantum computation. While conventional methods use a number of extra qubits that are linear in the weight of the syndrome, several improvements have been introduced using flag gadgets. In this work, we develop a f...

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Main Authors: Benjamin Anker, Milad Marvian
Format: Article
Language:English
Published: American Physical Society 2024-12-01
Series:PRX Quantum
Online Access:http://doi.org/10.1103/PRXQuantum.5.040340
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author Benjamin Anker
Milad Marvian
author_facet Benjamin Anker
Milad Marvian
author_sort Benjamin Anker
collection DOAJ
description Fault-tolerant syndrome extraction is a key ingredient in implementing fault-tolerant quantum computation. While conventional methods use a number of extra qubits that are linear in the weight of the syndrome, several improvements have been introduced using flag gadgets. In this work, we develop a framework to design flag gadgets using classical codes. Using this framework, we show how to perform fault-tolerant syndrome extraction for any stabilizer code with arbitrary distance using exponentially fewer qubits than conventional methods when qubit measurement and reset are relatively slow compared to a round of error correction. In particular, our method requires only (2t+1)t⌈log_{2}⁡(w)⌉ flag qubits to fault-tolerantly measure a weight-w stabilizer. We further take advantage of the saving provided by our construction to fault-tolerantly measure multiple stabilizers using a single gadget and show that it maintains the same exponential advantage when it is used to fault-tolerantly extract the syndromes of quantum low-density parity-check codes. Using the developed framework, we perform computer-assisted search to find several small examples where our constructions reduce the number of qubits required. These small examples may be relevant to near-term experiments on small-scale quantum computers.
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spelling doaj-art-e05f909b7a074591a8232140632691b92025-08-20T01:59:14ZengAmerican Physical SocietyPRX Quantum2691-33992024-12-015404034010.1103/PRXQuantum.5.040340Flag Gadgets Based on Classical CodesBenjamin AnkerMilad MarvianFault-tolerant syndrome extraction is a key ingredient in implementing fault-tolerant quantum computation. While conventional methods use a number of extra qubits that are linear in the weight of the syndrome, several improvements have been introduced using flag gadgets. In this work, we develop a framework to design flag gadgets using classical codes. Using this framework, we show how to perform fault-tolerant syndrome extraction for any stabilizer code with arbitrary distance using exponentially fewer qubits than conventional methods when qubit measurement and reset are relatively slow compared to a round of error correction. In particular, our method requires only (2t+1)t⌈log_{2}⁡(w)⌉ flag qubits to fault-tolerantly measure a weight-w stabilizer. We further take advantage of the saving provided by our construction to fault-tolerantly measure multiple stabilizers using a single gadget and show that it maintains the same exponential advantage when it is used to fault-tolerantly extract the syndromes of quantum low-density parity-check codes. Using the developed framework, we perform computer-assisted search to find several small examples where our constructions reduce the number of qubits required. These small examples may be relevant to near-term experiments on small-scale quantum computers.http://doi.org/10.1103/PRXQuantum.5.040340
spellingShingle Benjamin Anker
Milad Marvian
Flag Gadgets Based on Classical Codes
PRX Quantum
title Flag Gadgets Based on Classical Codes
title_full Flag Gadgets Based on Classical Codes
title_fullStr Flag Gadgets Based on Classical Codes
title_full_unstemmed Flag Gadgets Based on Classical Codes
title_short Flag Gadgets Based on Classical Codes
title_sort flag gadgets based on classical codes
url http://doi.org/10.1103/PRXQuantum.5.040340
work_keys_str_mv AT benjaminanker flaggadgetsbasedonclassicalcodes
AT miladmarvian flaggadgetsbasedonclassicalcodes