Experimental repetitive quantum channel simulation

Abstract

Universal control of quantum systems is a major goal to be achieved for quantum information processing, which demands thorough understanding of fundamental quantum mechanics and promises applications of quantum technologies. So far, most studies concentrate on ideally isolated quantum systems governed by unitary evolutions, while practical quantum systems are open and described by quantum channels due to their inevitable coupling to environment. Here, we experimentally simulate arbitrary quantum channels for an open quantum system, i.e. a single photonic qubit in a superconducting quantum circuit. The arbitrary channel simulation is achieved with minimum resource of only one ancilla qubit and measurement-based adaptive control. By repetitively implementing the quantum channel simulation, we realize an arbitrary Liouvillian for a continuous evolution of an open quantum system for the first time. Our experiment provides not only a testbed for understanding quantum noise and decoherence, but also a powerful tool for full control of practical open quantum systems.arXiv:1807.07694v1 [quant-ph]

Quantum generative adversarial learning in a superconducting quantum circuit

“…Figure 3 (A to C) shows the typical results for the experimental QGAN with σ = | g 〉〈 g | of the transmon qubit, the highest purity state that can be achieved in the experiment, as an example for the quantum true data. Since a quantum channel simulator can generate an arbitrary quantum state ( 25 ), the QGAN experiments by taking an arbitrary mixed state of the transmon as the true data is also studied, and the results are depicted in Fig. 3 (D to F).…”

“…In our superconducting architecture, the bosonic mode actually provides a quantum system with infinite dimensions, which can be encoded as a multilevel system. On the basis of the same adaptive technique used in our current experiment, an arbitrary quantum state of a photonic qudit with m levels (equivalent to a log 2 m -qubit system) can be generated and manipulated with the assistance of the transmon qubit ( 25 ). Then, our experiment can be straightforwardly extended to this photonic qudit that serves as either the quantum true or generated data.…”

“…The transmon qubit has an energy relaxation time T 1 = 30 μs and a pure dephasing time T φ = 120 μs, and its quantum state serves as either ρ or σ alternatively during the QGAN algorithm. The long-lived cavity has a photon lifetime T 1 = 143 μs and serves as an ancillary photonic qubit to facilitate the creation of the quantum true data σ in an arbitrary state through a quantum channel simulator ( 25 ). In ( 25 ), we showed that an arbitrary quantum state of the photonic qubit can be generated deterministically, which can be mapped back onto the transmon qubit for the initial σ.…”

Simulating Finite-Time Isothermal Processes with Superconducting Quantum Circuits

“…In quantum thermodynamics, the concerned system, as an open quantum system, generally evolves with the coupling to the environment. Simulations of open quantum systems have been proposed theoretically in terms of quantum channels [ 17 , 18 , 19 , 20 , 21 ], and realized experimentally on various systems, e.g., trapped ions [ 22 ], photons [ 23 ], nuclear spins [ 24 ], superconducting qubits [ 25 ], and IBM quantum computer recently [ 26 , 27 ]. The previous works mainly focus on simulating fixed open quantum systems, where the parameters of the systems are fixed with the evolution governed by a time-independent master equation.…”

“…In the adiabatic process, the parameter tuning is performed virtually with the unitary evolution implemented by quantum gates. In the isochoric process, the dissipative evolution is carried out with quantum channel simulation [ 23 , 25 , 39 , 40 , 41 , 42 ] with ancillary qubits, which play the role of the environments [ 18 , 21 , 26 ]. With this approach, we achieve the simulation of the isothermal process on the generic quantum computing system without physically tuning the control parameters.…”