Measurement-induced quantum phases realized in a trapped-ion quantum computer

Many-body open quantum systems balance internal dynamics against decoherence and measurements induced by interactions with an environment 1 , 2 . Quantum circuits composed of random unitary gates with interspersed projective measurements represent a minimal model to study the balance between unitary...

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Bibliographic Details
Published in:Nature physics 2022-07, Vol.18 (7), p.760-764
Main Authors: Noel, Crystal, Niroula, Pradeep, Zhu, Daiwei, Risinger, Andrew, Egan, Laird, Biswas, Debopriyo, Cetina, Marko, Gorshkov, Alexey V., Gullans, Michael J., Huse, David A., Monroe, Christopher
Format: Article
Language:English
Subjects:
639/766/119/2795
639/766/483/481
Atomic
Circuits
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Critical point
Error correction
Fault tolerance
Initial conditions
Letter
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Phase transitions
Phases
Physics
Physics and Astronomy
Purification
Quantum computers
Quantum computing
Theoretical
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Summary:Many-body open quantum systems balance internal dynamics against decoherence and measurements induced by interactions with an environment 1 , 2 . Quantum circuits composed of random unitary gates with interspersed projective measurements represent a minimal model to study the balance between unitary dynamics and measurement processes 3 – 5 . As the measurement rate is varied, a purification phase transition is predicted to emerge at a critical point akin to a fault-tolerant threshold 6 . Here we explore this purification transition with random quantum circuits implemented on a trapped-ion quantum computer. We probe the pure phase, where the system is rapidly projected to a pure state conditioned on the measurement outcomes, and the mixed or coding phase, where the initial state becomes partially encoded into a quantum error correcting codespace that keeps the memory of initial conditions for long times 6 , 7 . We find experimental evidence of the two phases and show numerically that, with modest system scaling, critical properties of the transition emerge. Many-body open quantum systems are predicted to undergo a phase transition towards a pure state through frequent projective measurements. The phases separated by this transition have now been observed with random circuits on a trapped-ion computer.
ISSN:1745-2473
1745-2481
DOI:10.1038/s41567-022-01619-7