Experimentally simulating the dynamics of quantum light and matter at deep-strong coupling

Abstract

The quantum Rabi model describing the fundamental interaction between light and matter is a cornerstone of quantum physics. It predicts exotic phenomena like quantum phase transitions and ground-state entanglement in ultrastrong and deep-strong coupling regimes, where coupling strengths are comparable to or larger than subsystem energies. Demonstrating dynamics remains an outstanding challenge, the few experiments reaching these regimes being limited to spectroscopy. Here, we employ a circuit quantum electrodynamics chip with moderate coupling between a resonator and transmon qubit to realise accurate digital quantum simulation of deep-strong coupling dynamics. We advance the state of the art in solid-state digital quantum simulation by using up to 90 second-order Trotter steps and probing both subsystems in a combined Hilbert space dimension of ∼80, demonstrating characteristic Schrödinger-cat-like entanglement and large photon build-up. Our approach will enable exploration of extreme coupling regimes and quantum phase transitions, and demonstrates a clear first step towards larger complexities such as in the Dicke model.

Quantum Simulation of the Quantum Rabi Model in a Trapped Ion

“…The phenomenon of photon number wave packets bouncing back and forth along the parity chains [19] has been observed in a classical simulator of a photonic waveguide system [26] and in analog and digital quantum simulations in cQED systems [27,28]. However, the study of the ground state in DSC regime is still an open challenge [22].…”

Superradiant phase transition in the ultrastrong-coupling regime of the two-photon Dicke model

“…Indeed, the SPT has been observed in driven atomic systems which effectively reproduce the DM [25][26][27]. In general, driven atomic or solid state systems represent a powerful tool to access the USC regime of quantum optical models, both in few [28][29][30][31][32] and many-body physics [33,34]. In the USC regime, even * louis.garbe@ens-lyon.fr apparently simple models entail a very complex physics.…”

Approaching ultrastrong coupling in transmon circuit QED using a high-impedance resonator

“…[12,13], experiments in the DSC regime have now been achieved with flux qubits coupled to resonators [14] as well as an electromagnetic continuum [15]. Additionally, the U/DSC coupling regime of the Rabi model was the subject of recent analog quantum simulations [16,17].…”