Strong Magnetic Coupling of an Ultracold Gas to a Superconducting Waveguide Cavity

Abstract

Placing an ensemble of 10 6 ultracold atoms in the near field of a superconducting coplanar waveguide resonator (CPWR) with Q ∼ 10 6 one can achieve strong coupling between a single microwave photon in the CPWR and a collective hyperfine qubit state in the ensemble with g eff /2π ∼ 40 kHz larger than the cavity line width of κ/2π ∼ 7 kHz. Integrated on an atomchip such a system constitutes a hybrid quantum device, which also can be used to interconnect solid-state and atomic qubits, to study and control atomic motion via the microwave field, observe microwave super-radiance, build an integrated micro maser or even cool the resonator field via the atoms.PACS numbers: 42.50.Pq, 37.30.+i In the past decade important breakthroughs in implementing quantum information processing were reached in different physical implementations [1], each showing advantages and shortcomings. For quantum information to emerge as a valuable technology, it is mandatory to pool their strengths. Solid-state systems allow fast processing and dense integration; atom or ion based systems are slower but exhibit long qubit coherence times. Ensembles of atoms constitute a quantum memory, it can be read out onto photons [2] which can then be transmitted over long distances [3]. Here we analyze a device to quantum interconnect superconducting solid-state qubits to an atomic quantum memory.The challenge in transferring the state of a solidstate qubit to atoms is bridging the tremendous gap in time scales that govern solid-state and atomic physics devices. This difference can be overcome using a coplanar waveguide resonator (CPWR) [4,5,6], which can be electrically coupled to single superconducting qubits [7,8,9,10,11]. Various ways were proposed to couple to atomic and molecular systems [12,13,14,15,16,17,18]. The small effective mode volume together with the long photon lifetime allow a strong coupling.The superconducting qubit to CPWR coupling has been implemented and studied by several groups [7,8,9,10,11]. In this letter we concentrate on the magnetic coupling of a microwave photon in a CPWR to a collective hyperfine qubit in an ensemble of ultracold atoms. We show below that even though the magnetic coupling strength is much weaker than the optical dipole coupling, one can achieve strong coupling with currently available technology of circuit cavity quantum electro dynamics and ultracold atomic ensembles on an atomchip.As particular qubit example we consider a hyperfine transition in 87 Rb between |F = 2, m F and |F = 1, m F states which frequency of 6.83 GHz being ideally suited for a CPWR. In principle both systems can be integrated in a hybrid device on an single su- perconducting atomchip [19,20]. Besides the transfer of a single photon to the atomic ensemble as a quantum memory and back, such a hybrid quantum system opens up many different other possibilities. For example nondestructive microwave detection of the atomic density will allow to continuously monitor BEC formation or changing operating parameters one can achieve a superrad...

Trapping of ultracold atoms in a 3He/4He dilution refrigerator

“…This apparatus provides the required experimental conditions for the realization of hybrid quantum systems [6,7] combining ultracold gases and superconducting quantum devices, and also for fundamental studies on ultra cold Rydberg atoms in absence of detrimental thermal radiation [32].…”

“…The development of cold atom/solid state hybrid systems holds the promise of creating a quantum interface between printed electronic circuits, atoms and light [1][2][3][4][5][6][7][8][9][10] with applications in quantum electronics and information processing. Several groups are currently preparing cold atomic clouds in the vicinity of superconducting chips at 77 K, cooled by liquid nitrogen, and at 4 K, cooled by liquid 4 He [11][12][13][14][15][16][17][18][19][20][21][22][23].…”

Monitoring entanglement evolution and collective quantum dynamics

“…For this purpose, we exemplarily investigate an "atomic cloud" containing a large number of atoms as described in Ref. 46. There, an ensemble of cold atoms interacting with a superconducting cavity, described by the Dicke model, was investigated.…”

“…In order to be specific, we evaluate φ 0 hf for the parameters 46 δ/2πh = 6.8GHz, α = 6 × 10 −5 , /2π = 20 GHz. This yields an effective single-atom coupling to the ohmic environment of αδ/2πh ≈ 0.4 MHz.…”

Heating rate and spin flip lifetime due to near-field noise in layered superconducting atom chips

“…In the area of magnetic trapping of ultracold atoms, considerable attention has been recently devoted to the interaction of atomic clouds with the surfaces of both superconducting atom chips [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and superconducting solid state devices [17][18][19][20]. Technological advances will allow a new generation of fundamental experiments and applications involving the control of the interface between atomic systems and quantum solid state devices.…”