Coherent coupling of a single spin to microwave cavity photons

Abstract

Electron spins and photons are complementary quantum-mechanical objects that can be used to carry, manipulate and transform quantum information. To combine these resources, it is desirable to achieve the coherent coupling of a single spin to photons stored in a superconducting resonator. Using a circuit design based on a nanoscale spin-valve, we coherently hybridize the individual spin and charge states of a double quantum dot while preserving spin coherence. This scheme allows us to achieve spin-photon coupling up to the MHz range at the single spin level. The cooperativity is found to reach 2.3, and the spin coherence time is about 60ns. We thereby demonstrate a mesoscopic device suitable for nondestructive spin read-out and distant spin coupling.The methods of cavity quantum electrodynamics hold promise for an efficient use of the spin degree of freedom in the context of quantum computation and simulation (1). Realizing a coherent coupling between a single spin and cavity photons could enable quantum nondemolition readout of a single spin, quantum spin manipulation, and facilitate the coupling of distant spins (1,2,3,4). It could also be used in hybrid architectures in which single spins are coupled to superconducting quantum bits (5), or to simulate one-dimensional spin chains (6).The natural coupling of a spin to the magnetic part of the electromagnetic field is weak (7). In order to enhance it, one needs a large spin ensemble, typically of about 10 12 spins (8,9,10,11,12,13), but these ensembles lose the intrinsic non-linearity of a single spin 1/2.Alternatively, several theoretical proposals have been put forward to electrically couple single spins to superconducting resonators in a mesoscopic circuit (14,15,16,17), building on the exquisite accuracy with which superconducting circuits can be used to couple superconducting qubits and photons and manipulate them (18). One such approach is to engineer an artificial spin-photon interaction by using ferromagnetic reservoirs (15).Noteworthy, the spin/photon coupling is also raising experimental efforts in the optical domain (19,20,21,22,23), but the circuit approach presents the significant advantage of scalability.Recent experiments have demonstrated the coupling of double quantum dot charge states to coplanar waveguide resonators, with a coupling strength gcharge ≈ 2  10 -50 MHz (24,25,26,27,28). In Ref,(29), the spin blockade read-out technique in quantum dots (30) was combined with charge sensing with a microwave resonator (31). In contrast to this spinblockade scheme, here we use the ferromagnetic proximity effect in a coherent conductor to engineer a spin-photon coupling. Our scheme relies on the use of a non collinear spin valve geometry, which realizes an artificial spin orbit interaction (15). Specifically, we contact two non collinear ferromagnets on a carbon nanotube double quantum dot.Our device is shown in Fig. 1, A-C. Our resonator is similar to a previous experiment (27) with a coupling scheme adapted from (24). It is a Nb resonator with a qua...

Collective non-perturbative coupling of 2D electrons with high-quality-factor terahertz cavity photons

“…De, 76.40.+b, 78.47.jh Strong resonant light-matter coupling in a cavity setting is an essential ingredient in fundamental cavity quantum electrodynamics (QED) studies [14] as well as in cavity-QED-based quantum information processing [8,9]. In particular, a variety of solid-state cavity QED systems have recently been examined [15][16][17][18], not only for the purpose of developing scalable quantum technologies, but also for exploring novel many-body effects inherent to condensed matter. For example, collective √ N -fold enhancement of light-matter coupling in an N -body system [19], combined with colossal dipole moments available in solids, compared to traditional atomic systems, is promising for entering uncharted regimes of ultrastrong light-matter coupling.…”

“…Strong coupling is achieved when the splitting, 2g, is much larger than the linewidth, (κ + γ)/2, and ultrastrong coupling is achieved when g becomes a considerable fraction of ω 0 . The two standard figures of merit to measure the coupling strength are C ≡ 4g 2 /(κγ) and g/ω 0 ; here, C is called the cooperativity parameter [18], which is also the determining factor for the onset of optical bistability through resonant absorption saturation [20]. In order to maximize C and g/ω 0 , one should construct a cavity QED setup that combines a large dipole moment (i.e., large g), a small decoherence rate (i.e., small γ), a large cavity Q factor (i.e., small κ), and a small resonance frequency ω 0 .…”

Circuit quantum electrodynamics architecture for gate-defined quantum dots in silicon

“…3(c) and 3(d), we plot A=A 0 and D/ as a function of for the ðN 1 þ 1; N 2 Þ $ ðN 1 ; N 2 þ 1Þ interdot charge transition. These data are fit to the cavity input-output theory 17,18 using the measured values of f c and j. Best fit parameters yield t c ¼ 16:4 leV, g c =2p ¼ 23 MHz, and a charge qubit decoherence rate c=2p ¼ 40 MHz.…”

“…In cQED systems with superconducting qubits, cavity photons are also widely used for dispersive state readout, as the significant electric dipole moments of these devices result in large phase shifts in the cavity response. 13,14 In semiconductor systems, hybrid cQED devices have been implemented using GaAs, 15,16 InAs, 17 carbon nanotube, 18 and graphene QDs. 19 There are several proposals pertaining to the coupling of Si spin qubits to cavities, 20,21 as well as the demonstration of a high kinetic inductance cavity, fabricated with the intention of coupling to Si quantum dots.…”

Lifting the Franck-Condon blockade in driven quantum dots

“…A further modification could be realized by incorporating the quantum dot into a setup related to circuit quantum electrodynamics (cQED), 37,38 thus replacing the drive from the gate voltage with one generated by a microwave cavity. Even more, cQED setups would also allow for replacing the classical drive (i.e.…”