Lifetime of Strongly Correlated States on Near-Term Quantum Computers.

Here we study the lifetime of strongly correlated stationary states on quantum computers. We find that these states develop a nontrivial time dependence due to the presence of noise on current devices. After an exciton-condensate state is prepared, its behavior is observed with respect to unitary operations that should preserve the stationarity of the state. Instead of stationarity, however, we observe nontrivial time dependence in which the large eigenvalue of the particle-hole reduced density matrix─the exciton population of the condensate─decays toward unity, reflecting the loss of entanglement and off-diagonal long-range order. The result offers insight into the challenge of simulating strongly correlated systems on near-term quantum devices and highlights the importance of developing novel strategies for error mitigation that can preserve many-body correlations.