Cavity and Circuit QED

Cavity and circuit quantum electrodynamics (cQED) describe the interaction between real or artificial atoms with quantized bosonic modes. Most often, I work in the domain of superconducting qubits, so my “atoms” are artificial, built from superconducting circuits, and my bosonic modes are electromagnetic in nature.

Despite decades of research in these fields, there are still many surprises left to be uncovered. For example, my PhD advisor and I developed a simple description for the state formed when the bosonic mode is coherently driven in the strong coupling, dispersive regime of the Jaynes-Cummings model [3], and showed how this limits the quantum non-demolition character of cQED qubit readout [4].

In my postdoctoral work, my collaborators and I demonstrated that with a different kind of bosonic drive, parametric (two-photon) driving, it is possible to enhance cQED coupling [1]. Beyond just enhancing gate-speeds in a quantum computer, this enables analogue simulation of the quantum Rabi model in the ultra-strong coupling regime.

In general, I’m interested in developing accurate and efficient models for cQED systems to aide my experimental collaborators in device design and operation. At a higher level, I care about the impact of architectural questions, like the definition of the measurement basis versus the operational basis, and of non-leading order interactions, such as stray-couplings. How the small errors these issues cause accumulate over time during a computation, or in space as systems grow, is also of particular interest to me.

Selected Papers

  1. C. Leroux, L. C. G. Govia, and A. A. Clerk, Enhancing cavity QED via anti-squeezing: synthetic ultra-strong coupling, Phys. Rev. Lett. 120 (9), 093602 (2018).

  2. C. Leroux, L. C. G. Govia, and A. A. Clerk, Simple variational ground state and pure cat state generation in the quantum Rabi model, Phys. Rev. A 96 (4), 043834 (2017).

  3. L. C. G. Govia and F. K. Wilhelm, Entanglement generated by the dispersive interaction: The dressed coherent state, Phys. Rev. A 93 (1), 012316 (2016).

  4. L. C. G. Govia and F. K. Wilhelm, Unitary-feedback-improved qubit initialization in the disper- sive regime, Phys. Rev. Applied 4, 054001 (2015).

  5. L. C. G. Govia, E. J. Pritchett, and F. K. Wilhelm, Generating nonclassical states from classical radiation by subtraction measurements, New J. Phys. 16, 045011 (2014).