Verified quantum information scrambling

Abstract

Quantum scrambling is the dispersal of local information into many-body quantum entanglements and correlations distributed throughout the entire system. This concept underlies the dynamics of thermalization in closed quantum systems, and more recently has emerged as a powerful tool for characterizing chaos in black holes [1][2][3][4][5]. However, the direct experimental measurement of quantum scrambling is difficult, owing to the exponential complexity of ergodic many-body entangled states. One way to characterize quantum scrambling is to measure an out-of-time-ordered correlation function (OTOC); however, since scrambling leads to their decay, OTOCs do not generally discriminate between quantum scrambling and ordinary decoherence. Here, we implement a quantum circuit that provides a positive test for the scrambling features of a given unitary process [6,7]. This approach conditionally teleports a quantum state through the circuit, providing an unambiguous litmus test for scrambling while projecting potential circuit errors into an ancillary observable. We engineer quantum scrambling processes through a tunable 3-qubit unitary operation as part of a 7-qubit circuit on an ion trap quantum computer. Measured teleportation fidelities are typically ∼ 80%, and enable us to experimentally bound the scrambling-induced decay of the corresponding OTOC measurement.

Towards analog quantum simulations of lattice gauge theories with trapped ions

“…Trapped ions provide a pristine platform for quantum simulations [18]. Given the extremely high level of control enabled by laser-cooled and localized ions confined by electromagnetic fields, exceedingly high fidelities in state preparation and measurement, all-to-all entangling capability enabled through control over the excitations of the motional normal modes, and scalability potential of such systems, this architecture has become a primary candidate for digital quantum computations in recent years [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. A unique feature of the trapped ion architecture is that global addressing of the ions using a few laser beams allows the realization of tunable longrange spin-spin interactions in the chain.…”

A random unitary circuit model for black hole evaporation

“…[83] within a quantum teleportation protocol related to the setting of this paper, see also Ref. [84] for an experimental implementation. Furthermore, we note that the Hayden-Preskill protocol with a U (1) conserved charge has been studied before in Ref.…”

Properties of phonon modes of an ion-trap quantum computer in the Aubry phase

“…In 2019, the ion quantum computers demonstrated an impressive boost with realizations of several quantum algorithms with up to 11 qubits [10][11][12][13][14]. Hybrid classicalquantum algorithms have even been realized with up to 20 qubits [15].…”