Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session W6: Progress on Quantum Optics with Circuit Quantum Electrodynamics |
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Sponsoring Units: GQI Chair: Steve Girwin, Yale University Room: 406 |
Thursday, March 19, 2009 11:15AM - 11:51AM |
W6.00001: Controlling Photons, Qubits and their Interactions in Superconducting Electronic Circuits Invited Speaker: A combination of ideas from atomic physics, quantum optics and solid state physics allows us to investigate the fundamental interaction of matter and light on the level of single quanta in electronic circuits. In an approach known as circuit quantum electrodynamics, we coherently couple individual photons stored in a high quality microwave frequency resonator to a fully controllable superconducting two-level system (qubit) realized in a macroscopic electronic circuit [1]. In particular, we have recently observed the simultaneous interaction of one, two and three photons with a single qubit. In these experiments, we have probed the quantum nonlinearity of the qubit/light interaction governed by the Jaynes-Cummings hamiltonian, clearly demonstrating the quantization of the radiation field in the on-chip cavity. We have also performed quantum optics experiments with no photons at all. In this situation, i.e. in pure vacuum, we have resolved the renormalization of the qubit transition frequency - known as the Lamb shift - due to its non-resonant interaction with the cavity vacuum fluctuations [3].\\[4pt] [1] A. Wallraff et al., Nature (London) 431, 162 (2004)\\[0pt] [2] J. Fink et al., Nature (London) 454, 315 (2008)\\[0pt] [3] A. Fragner et al., Science 322, 1357 (2008) [Preview Abstract] |
Thursday, March 19, 2009 11:51AM - 12:27PM |
W6.00002: Nonlinear response of the vacuum Rabi resonance Invited Speaker: On the level of single atoms and photons, the coupling between atoms and the electromagnetic field is typically very weak. By employing a cavity to confine the field, the strength of this interaction can be increased many orders of magnitude to a point where it dominates over any dissipative process. This strong-coupling regime of cavity quantum electrodynamics has been reached for real atoms in optical cavities, and for artificial atoms in circuit QED and quantum-dot systems. A signature of strong coupling is the splitting of the cavity transmission peak into a pair of resolvable peaks when a single resonant atom is placed inside the cavity -- an effect known as vacuum Rabi splitting. The circuit QED architecture is ideally suited for going beyond this linear response effect. Here, we show that increasing the drive power results in two unique nonlinear features in the transmitted heterodyne signal: the supersplitting of each vacuum Rabi peak into a doublet, and the appearance of additional peaks with the characteristic $\sqrt{n}$ spacing of the Jaynes-Cummings ladder. These constitute direct evidence for the coupling between the quantized microwave field and the anharmonic spectrum of a superconducting qubit acting as an artificial atom. Work done in collaboration with L.S. Bishop, J.M. Chow, A.A. Houck, M.H. Devoret, E. Thuneberg, S.M. Girvin, and R.J. Schoelkopf. [Preview Abstract] |
Thursday, March 19, 2009 12:27PM - 1:03PM |
W6.00003: Preparation of arbitrary quantum states in a microwave resonator Invited Speaker: Two-level systems, or qubits, can be prepared in arbitrary quantum states with exquisite control, just using classical electrical signals. Achieving the same degree of control over harmonic resonators has remained elusive, due to their infinite number of equally spaced energy levels. Here we exploit the good control over a superconducting phase qubit by using it to pump photons into a high-$Q$ coplanar wave guide resonator and, subsequently, to read out the resonator state. This scheme has previously allowed us to prepare and detect photon number states (Fock states) in the resonator [1]. Using a generalization of this scheme [2] we can now create arbitrary quantum states of the photon field with up to approximately 10 photons. We analyze the prepared states by mapping out the corresponding Wigner function, which is the phase-space equivalent to the density matrix and provides a complete description of the quantum state.\\[2ex] [1] MH {\it et al.}, Nature {\bf 454}, 310 (2008)\\[1ex] [2] Law and Eberly, Phys.\ Rev.\ Lett.\ {\bf 76} 1055 (1996) [Preview Abstract] |
Thursday, March 19, 2009 1:03PM - 1:39PM |
W6.00004: Resonant Two-Qubit Gates and Mesoscopic Shelving Qubit Readout in Circuit QED Invited Speaker: We consider the implementation of universal sets of resonant one-qubit and two-qubit gates for superconducting qubits inside microwave resonators in Circuit QED, aiming at the speed-up of gate operations [1]. We study also the implementation of mesoscopic shelving readout of a superconducting qubit inside a microwave resonator, where a high-fidelity measurement may be achieved [2]. In both proposals we borrow from inspiring quantum-optical tools and concepts, exploiting the advantages of three-level physics and adapting electron-shelving readout in a novel manner in the context of multi-cavity physics [3], and in particular two-cavity Circuit QED [4]. \\[4pt] REFERENCES: \\[0pt] [1] G. Haack, F. Helmer, M. Mariantoni, J. von Delft, F. Marquardt, and E. Solano, ``Resonant toolbox of universal quantum gates in Circuit QED'', in preparation. \\[0pt] [2] B. Englert, G. Mangano, M. Mariantoni, R. Gross, J. Siewert, and E. Solano, ``Mesoscopic Shelving Qubit Readout in Circuit QED'', in preparation. \\[0pt] [3] F. Helmer, M. Mariantoni, A. G. Fowler, J. von Delft, E. Solano, and F. Marquardt, ``Two-dimensional cavity grid for scalable quantum computation with superconducting circuits'', arXiv:0706.3625. \\[0pt] [4] M. Mariantoni, F. Deppe, A. Marx, R. Gross, F. K. Wilhelm, and E. Solano, ``Two-resonator circuit quantum electrodynamics: A superconducting quantum switch'', Phys. Rev. B 78, 104508 (2008). [Preview Abstract] |
Thursday, March 19, 2009 1:39PM - 2:15PM |
W6.00005: Lasing, Cooling, and Nonequilibrium Photon States in Circuit QED Invited Speaker: Several of the concepts originally introduced in quantum electrodynamics (QED) have been reproduced and extended in recent experiments with superconducting quantum circuits. In these systems a single qubit (or few) is coupled to a microwave resonator. Lasing and cooling of the resonator as well as nonequilibrium photon states, incl. Fock states, have been observed. Apart from the similarities to quantum optics there exist important differences, some of which will be addressed in this talk: (i) Circuit QED provides realizations of ``single-atom lasers,'' with the atom being replaced by a superconducting qubit. The low number of degrees of freedom makes the quantum nature of the field visible. As a result in single atom lasers the lasing transition is smeared. On the other hand, the permanent qubit - resonator coupling allows exploring the specific properties of single-atom lasing. (ii) The coupling between qubit and resonator may be very strong, giving rise to qualitatively new effects. For instance, strong coupling can lead to multiple optimal regimes for lasing and a double peak structure in the resonator output spectrum. In addition higher order correlations gain quantitative importance. (iii) Decoherence and relaxation effects need to be accounted for. The large line-width observed in single-qubit lasers is mainly due to low-frequency noise, which renders the line-shape Gaussian rather than Lorentzian. (iv) Circuit QED offers new ways to drive the qubit, e.g., the qubit may consist of a driven superconducting single-electron transistor, or to engineer resonators with specific anharmonicities. (v) A variety of resonant conditions can be exploited, including the situation where the low Rabi-frequency is in resonance with a slow oscillator. [Preview Abstract] |
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