Proposal for a quantum interface between photonic and superconducting qubits

Abstract

We show that optically active coupled quantum dots embedded in a superconducting microwave cavity can be used to realize a fast quantum interface between photonic and transmon qubits. Single photon absorption by a coupled quantum dot results in generation of a large electric dipole, which in turn ensures efficient coupling to the microwave cavity. Using cavity parameters achieved in prior experiments, we estimate that bi-directional microwave-optics conversion in nanosecond timescales with efficiencies approaching unity is experimentally feasible with current technology. We also outline a protocol for in-principle deterministic quantum state transfer from a time-bin photonic qubit to a transmon qubit. Recent advances in quantum dot based quantum photonics technologies indicate that the scheme we propose could play a central role in connecting quantum nodes incorporating cavity-coupled superconducting qubits.Introduction. A quantum interface between flying photonic and stationary matter qubits is widely regarded as an essential element of quantum networks [1][2][3]. Remarkable advances over the last decade have established that circuit-QED, consisting of superconducting (SC) qubits non-perturbatively coupled to a common microwave (MW) cavity, is particularly promising for realization of small-scale quantum information processors [4,5]. The most prominent limitation in realization of quantum networks consisting of circuit-QED based processors is the difficulty in transferring quantum information over distances exceeding meters. Motivated by overcoming this roadblock, several groups have embarked on research aimed at creating a quantum interface between SC qubits and propagating photonic qubits. Among the several ingenuous proposals [6][7][8][9][10][11][12][13][14][15] to resolve this conundrum, the approach based on using optomechanical coupling [16][17][18][19][20] has proven to be particularly successful: pioneering experiments have demonstrated conversion efficiency of 10% with a bandwidth of 30 kHz [20]. A limitation for most if not all of these approaches is the relatively small effective coupling strength between the single optical and MW photons, which in turn prevents conversion of quantum information on time-scales much shorter than typical SC qubit coherence times.

Low-loss high-impedance circuit for quantum transduction between optical and microwave photons

“…The corresponding decay time is 1/κ = 88 ns (κ/2π = 1.8 MHz). This low microwave resonator loss rate ensures that the resonator photon decay time is much longer than the time necessary for the optical-microwave transduction process (∼several ns [22]) and a swap operation time (∼10 ns [37]) between a transmon and a microwave resonator. This low-loss feature facilitates the efficient transduction between an optical and microwave qubit.…”

“…The optically excited exciton with voltage tunable indirect exciton content [15] has a large electric dipole moment, which efficiently interacts with the microwave electric field oriented in the same direction. For the detailed transduction scheme, see references [16,22]. Since the design of the circuit is compatible with the integration of typical superconducting qubits, one could incorporate a superconducting qubit into another antinode of the resonator and perform qubit-to-optical photon transduction via the QDM and the resonator bath.…”

Cavity-enhanced Raman heterodyne spectroscopy in Er3+:Y2SiO5 for microwave to optical signal conversion

“…Electroopic approaches [14,15,19] have achieved 0.1% quantum efficiencies with megahertz bandwiths [20] using an optical whispering gallery mode resonator made of lithium niobate. Faraday rotation and ferromagnetic resonance in yttrium iron garnet (YIG) has been explored [21][22][23], as well as using Rydberg atoms [24,25] and quantum dots [26]. This work follows theoretical proposals for microwave-optical conversion using rare earth ions in solids [27,28].…”

Enhancing quantum transduction via long-range waveguide-mediated interactions between quantum emitters

“…Similar propsals have been considerd in Refs. [27,28], but as discussed above the current approach takes advantage of the demonstrated high coupling efficiency in waveguides and avoids the need for engineering near field interactions. To get an estimate for the magnitude of the electric coupling g s between a SC qubit and a QD, we numerically simulate the electric field for a Cooper pair box (CPB) island of dimensions 700 × 200 × 20 nm, similar to Ref.…”

“…As a particular application we show how to exploit the proposed transducer as a quantum interface between optical photons and superconducting qubits. Related approaches were recently proposed using two nearby dipole-coupled molecules [27] or a double QD molecule [28]. As opposed to these systems, experimental demonstrations of QD-waveguide interfaces have shown more efficient coherent coupling to traveling light fields [26].…”