Kavli Affiliate: Matthew P. A. Fisher
| First 5 Authors: Hirsh Kamakari, Jiace Sun, Yaodong Li, Jonathan J. Thio, Tanvi P. Gujarati
| Summary:
Quantum systems subject to random unitary evolution and measurements at
random points in spacetime exhibit entanglement phase transitions which depend
on the frequency of these measurements. Past work has experimentally observed
entanglement phase transitions on near-term quantum computers, but the
characterization approach using entanglement entropy is not scalable due to
exponential overhead of quantum state tomography and postselection. Recently,
an alternative protocol to detect entanglement phase transitions using linear
cross entropy was proposed, attempting to eliminate both bottlenecks. Here, we
report demonstrations of this protocol in systems with one-dimensional and
all-to-all connectivities on IBM’s quantum hardware on up to 22 qubits, a
regime which is presently inaccessible if postselection is required. We
demonstrate data collapses onto scaling functions with critical exponents in
semiquantitative agreement with theory. Our demonstration of the cross entropy
benchmark (XEB) protocol paves the way for studies of measurement-induced
entanglement phase transitions and associated critical phenomena on larger
near-term quantum systems.
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