Single-qubit lasing in the strong-coupling regime

Abstract

Motivated by recent "circuit QED" experiments we study the lasing transition and spectral properties of single-qubit lasers. In the strong coupling, low-temperature regime quantum fluctuations dominate over thermal noise and strongly influence the linewidth of the laser. When the qubit and the resonator are detuned, amplitude and phase fluctuations of the radiation field are coupled, and the phase diffusion model, commonly used to describe conventional lasers, fails. We predict pronounced effects near the lasing transition, with an enhanced linewidth and non-exponential decay of the correlation functions. We cover a wide range of parameters by using two complementary approaches, one based on the Liouville equation in a Fock state basis, covering arbitrarily strong coupling but limited to low photon numbers, the other based on the coherent-state representation, covering large photon numbers but restricted to weak or intermediate coupling.

Phonon cooling and lasing with nitrogen-vacancy centers in diamond

“…The first case ∼ (a + a † ) represents an off-resonant interaction, where only the energy of the driven excited state is modulated. This situation is similar to the coupling of nanomechanical systems to quantum dots or other solid-state two-level systems, where cooling [23][24][25][26]29 and lasing 32,35,37 have previously been discussed. The resulting cooling rate is optimized by choosing a laser detuning δ L = −ω m [see Fig.…”

“…In this paper, we consider the strain coupling between a single NV center and a single resonant mechanical mode of a diamond nanoresonator, and analyze ground-state cooling [23][24][25][26][27][28][29] and phonon lasing [30][31][32][33][34][35][36][37] techniques for manipulating the phonon mode in this system. Compared to previous proposals for using the strain coupling to natural and artificial two-level defects 23,37,38 to achieve this task, we here exploit the rich electronic structure of the NV center and focus on an approach involving two near-degenerate electronically excited states.…”

Cavity QED with hybrid nanocircuits: from atomic-like physics to condensed matter phenomena

“…The cooperativity can also be used to express the lasing threshold C e−ph 1/2 to obtain a lasing effect with a single qubit in a cavity, in a situation where ω ij = ω 0 and the qubit dephasing Γ * ϕ is much stronger than the qubit relaxation Γ 1 (Γ * ϕ Γ 1 so that Γ * 2 = Γ ϕ + (Γ 1 /2) Γ ϕ ) (see for instance Refs. 164,165 ). In the devices considered in the present review, Λ 0 Γ * 2 is always fulfilled due to the high quality of the resonators used.…”

Observation of the Three-State Dressed States in Circuit Quantum Electrodynamics

“…An advantage of using superconducting qubits is their large transition dipole moments, which enable strong coupling to the microwave field [10]. Exploiting this strong coupling, lasing experiments become possible by using a single quantum emitter: Maser operation has been demonstrated by a single driven qubit-cavity system [11,12] and a driven qubit coupled directly to a transmission line [13], where population inversion takes place in the bare-state basis. Amplification due to dressed-state inversion has been reported recently in a qubit-cavity system [14], and lasing without inversion independent of basis has also been proposed theoretically [15].…”