Dissipative mean-field theory of IBM utility experiment
In spite of remarkable recent advances, quantum computers have not yet found
any useful applications. A promising direction for such utility is offered by
the simulation of the dynamics of many-body quantum systems, which cannot be
efficiently computed classically. Recently, IBM used a superconducting quantum
computer to simulate a kicked quantum Ising model for large numbers of qubits
and time steps. By employing powerful error mitigation techniques, they were
able to obtain an excellent agreement with the exact solution of the model.
This result is very surprising, considering that the total error accumulated by
the circuit is prohibitively large. In this letter, we address this paradox by
introducing a dissipative mean-field approximation based on Kraus operators.
Our effective theory reproduces the many-body unitary dynamics and matches
quantitatively local and non-local observables. These findings demonstrate that
the observed dynamics is equivalent to a single qubit undergoing rotations and
dephasing. Our emergent description can explain the success of the quantum
computer in solving this specific problem.
Emanuele G. Dalla Torre Mor M. Roses