Abstract
The strong coupling limit of cavity quantum electrodynamics (QED) implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD) and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size at a resonator linewidth and a DQD charge qubit decoherence rate of extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.
- Received 16 January 2017
DOI:https://doi.org/10.1103/PhysRevX.7.011030
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Strong Light-Matter Coupling in a Hybrid System
Published 9 March 2017
A system combining a quantum dot and a superconducting cavity achieves the strongest light-matter coupling for this type of hybrid system.
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Popular Summary
Traditional digital technologies process information encoded in bits—binary numbers that take on one of two values. But by leveraging bizarre behavior of atomic particles, such as the ability to be in more than one state at once, quantum computers can tackle complex problems that traditional computers cannot. One essential ingredient for processing quantum information is the efficient transfer of energy across different systems. This transfer requires that one system be able to enact change in the other, faster than either state decays. We report on experiments in which we have reached this so-called “strong coupling regime”; these experiments show how circuit quantum electrodynamics (QED) experiments with semiconductor nanostructures can be used for both quantum information processing and fundamental studies of interactions between light and matter.
In our setup, we couple electrons trapped on nanoscale islands in a semiconductor to microwave photons confined in a superconducting resonator. Such a coupling has been shown before, but the strength of the coupling has been limited to around 25 MHz, an order of magnitude below typical decoherence rates in these systems. To achieve stronger couplings, we designed a resonator that exhibits enhanced vacuum fluctuations of the electric field due to an increased characteristic impedance. This approach enabled coupling strengths of up to 155 MHz, which, together with lowered decoherence rates of 40 MHz, placed the hybrid circuit firmly in the strong coupling regime.
Our approach yields the highest coupling strength reported to date for semiconductor-superconductor hybrid systems. The coupling strength can be engineered in a controlled manner, and the method can be applied to a variety of charge-based quantum systems. We expect that the technique should be useful for reading out qubit states and for developing two-qubit gates for electronic systems.