Measurement-based long-range entangling gates in constant depth

The depth of quantum circuits is a critical factor when running them on state-of-the-art quantum devices owing to their limited coherence times. Reducing circuit depth decreases noise in near-term quantum computations and reduces overall computation time. This also benefits fault-tolerant quantum co...

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Main Authors: Elisa Bäumer, Stefan Woerner
Format: Article
Language:English
Published: American Physical Society 2025-05-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.7.023120
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author Elisa Bäumer
Stefan Woerner
author_facet Elisa Bäumer
Stefan Woerner
author_sort Elisa Bäumer
collection DOAJ
description The depth of quantum circuits is a critical factor when running them on state-of-the-art quantum devices owing to their limited coherence times. Reducing circuit depth decreases noise in near-term quantum computations and reduces overall computation time. This also benefits fault-tolerant quantum computations. Here, we show how to reduce the depth of quantum subroutines that typically scale linearly with the number of qubits, such as quantum fan-out and long-range CNOT gates, to a constant depth using mid-circuit measurements and feedforward operations, while only requiring a 1D line topology. We compare our protocols with existing ones to highlight their advantages. Additionally, we verify the feasibility by implementing the measurement-based quantum fan-out gate and long-range CNOT gate on real quantum hardware, demonstrating significant improvements over their unitary implementations.
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spelling doaj-art-c4c30ab79f724472a8e45f5ea4b4b8ed2025-08-20T02:14:34ZengAmerican Physical SocietyPhysical Review Research2643-15642025-05-017202312010.1103/PhysRevResearch.7.023120Measurement-based long-range entangling gates in constant depthElisa BäumerStefan WoernerThe depth of quantum circuits is a critical factor when running them on state-of-the-art quantum devices owing to their limited coherence times. Reducing circuit depth decreases noise in near-term quantum computations and reduces overall computation time. This also benefits fault-tolerant quantum computations. Here, we show how to reduce the depth of quantum subroutines that typically scale linearly with the number of qubits, such as quantum fan-out and long-range CNOT gates, to a constant depth using mid-circuit measurements and feedforward operations, while only requiring a 1D line topology. We compare our protocols with existing ones to highlight their advantages. Additionally, we verify the feasibility by implementing the measurement-based quantum fan-out gate and long-range CNOT gate on real quantum hardware, demonstrating significant improvements over their unitary implementations.http://doi.org/10.1103/PhysRevResearch.7.023120
spellingShingle Elisa Bäumer
Stefan Woerner
Measurement-based long-range entangling gates in constant depth
Physical Review Research
title Measurement-based long-range entangling gates in constant depth
title_full Measurement-based long-range entangling gates in constant depth
title_fullStr Measurement-based long-range entangling gates in constant depth
title_full_unstemmed Measurement-based long-range entangling gates in constant depth
title_short Measurement-based long-range entangling gates in constant depth
title_sort measurement based long range entangling gates in constant depth
url http://doi.org/10.1103/PhysRevResearch.7.023120
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AT stefanwoerner measurementbasedlongrangeentanglinggatesinconstantdepth