Measurement-altered Ising quantum criticality

Understand

Quantum critical systems constitute appealing platforms for the exploration of novel measurement-induced phenomena due to their innate sensitivity to perturbations.

• We study the impact of measurement on paradigmatic Ising quantum critical chains using an explicit protocol, whereby correlated ancilla are entangled with the critical chain and then projectively measured.
• Using a perturbative analytic framework supported by extensive numerical simulations, we demonstrate that measurements can qualitatively alter long-distance correlations in a manner dependent on the choice of entangling gate, ancilla measurement basis, measurement outcome, and nature of ancilla correlations.
• We derive numerous quantitative predictions for the behavior of correlations in select measurement outcomes, and also identify two strategies for detecting measurement-altered Ising criticality in measurement-averaged quantities.