Emulating weak localization using a solid-state quantum circuit

Abstract

Quantum interference is one of the most fundamental physical effects found in nature. Recent advances in quantum computing now employ interference as a fundamental resource for computation and control. Quantum interference also lies at the heart of sophisticated condensed matter phenomena such as Anderson localization, phenomena that are difficult to reproduce in numerical simulations. Here, employing a multiple-element superconducting quantum circuit, with which we manipulate a single microwave photon, we demonstrate that we can emulate the basic effects of weak localization. By engineering the control sequence, we are able to reproduce the well-known negative magnetoresistance of weak localization as well as its temperature dependence. Furthermore, we can use our circuit to continuously tune the level of disorder, a parameter that is not readily accessible in mesoscopic systems. Demonstrating a high level of control, our experiment shows the potential for employing superconducting quantum circuits as emulators for complex quantum phenomena.

Steady-state phase diagram of a driven QED-cavity array with cross-Kerr nonlinearities

“…This freedom paves the way to explore a multitude of different engineered Hamiltonians with systems of cavities. At this point, it is also worth to stress that the implementation of cavity arrays within circuit-QED is very promising, the first experiments with arrays of up to five cavities have been done [43][44][45], and experiments with lattices of cavities are progressing fast [5].…”

Quantum systems under frequency modulation

“…One immediate application of this observation is in the realization of phase gates for quantum computing. Another application is quantum simulation: by changing randomly the detuning, one can emulate weak localization, with the detuning playing the role of the phase accumulated by an electron through scattering as it moves in a disordered medium [125]. Similar ideas can be used to simulate time-reversal symmetry and universal fluctuations, in this case by driving the system across the Landau-Zener transition using a bichromatic modulation [84,126].…”

Tunable and switchable coupling between two superconducting resonators

“…One way is to decouple two circuits by detuning them in frequency, for example by using the frequency tunability of superconducting qubits. With this technique, systems with up to five qubits and up to five microwave resonators were studied, [5][6][7] entangled quantum states were created [8][9][10] and quantum teleportation 11 and quantum computing protocols were demonstrated. [12][13][14] Alternatively, the coupling between two circuit QED building blocks can be mediated by additional coupling circuits.…”

“…[3][4][5] One of the most important advantages in using superconducting circuits for these purposes is the large coupling strength between the main building blocks, namely superconducting quantum bits and microwave resonators. Noticeably, the coupling strength remains considerable even for secondorder mechanisms.…”