Poster presentations
For
each poster presentation one poster wall will be
available.
These poster walls have the following size
(don't feel obliged to
really fill it):
Width:
97cm
Height: 250cm
Posters can be put
up for the full duration of the event. Discussions during the
breaks are encouraged.
| Gheeraert, Nicolas | Coherent state based exact dynamics of a qubit coupled to a chain of Josephson junctions | Abstract |
| Gosner, Jennifer | Quantum dynamics of a strongly driven Josephson junction | Abstract |
| Hazra, Dibyendu | High impedance environment for inelastic Cooper pair tunneling | Abstract |
| Maisi, Ville | Microwave emission from a gate-defined semiconductor charge qubit | Abstract |
| Meister, Selina | Non-linear classical dynamics in a superconducting circuit containing a cavity and a Josephson junction | Abstract |
| Mendes, Udson | Non-equilibrium properties of a microwave resonator coupled to a tunnel junction | Abstract |
| Coherent state based exact dynamics of a qubit coupled to a chain of Josephson junctions Gheeraert, Nicolas (CNRS, Institut NEEL, Nanosciences, Grenoble, France) |
We study the time-evolution of a quantum dot strongly coupled to a microwave photon bath that is supported by an array of Josephson junctions in circuit QED. The dynamics is considered in the framework of the spin-boson model for the system as a whole (qubit+bath), without tracing out the environment. Applying Dirac-Frenkel's variational principle to a coherent state decomposition of the wavefunction leads to simple dynamical equations, for which an efficient numerical algorithm is proposed. Various protocols are examined, such as a strong drive of the qubit itself (quantum quench), but also microwave irradiation within the chain (microwave photon transport). |
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| Quantum dynamics of a strongly driven Josephson Junction Gosner, Jennifer (Universität Ulm, Institute for complex quantum systems, Department of Physics , Ulm, Germany) |
A Josephson Junction embedded in a dissipative circuit can be driven to exhibit non-linear oscillations. Classically the non-linear oscillator shows under sufficiently strong driving and weak damping dynamical bifurcations and a bistable region similar to the conventional Duffing-oscillator. These features depend sensitively on initial conditions and parameters. The sensitivity of this circuit, called Josephson Bifurcation Amplifier, can be used to amplify an incoming signal, to form a sensing device or even for measuring a quantum system. The quantum dynamics can be described by a dissipative Lindblad master equation. Signatures of the classical bifurcation phenomena appear in the Wigner representation, used to characterize and visualize the resulting behaviour. In order to compare this quantum dynamics to that of the conventional Duffing-oscillator, the complete cosine-nonlinearity of the Josephson Junction is kept for the quantum description while going into a rotating frame. |
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| High impedance environment for inelastic Cooper pair tunneling Hazra, Dibyendu (CEA Grenoble, INAC/SPSMS/GT, SPSMS/LATEQ, Grenoble, France) |
Cooper pairs can tunneling through a small Josephson junction at finite bias voltage by emitting their energy 2eV into the electromagnetic environment of the junction. This can happen in the form of one or several photons. The multi-photon processes reveal the nonlinearity of the Josephson junction and can lead to nonclassical statistics of the emitted radiation. They become dominant over one-photon processes when the electromagnetic environment can be described by a mode with high characteristic impedance exceeding 2 kOhm. Here, we present the possibility to design such high impedance resonators as well as SIS Josephson junctions with large gap based on Niobium Nitride thin films with very large superconducting gap and high kinetic inductance. |
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| Microwave Emission from a Gate-Defined Semiconductor Charge Qubit Maisi, Ville (ETH Zürich, Zurich, Switzerland) |
We investigate a hybrid circuit quantum electrodynamics (QED) architecture in which a biased double quantum dot charge qubit emits photons into a nearby microwave cavity. Circuit QED has been a powerful approach to study excitations of superconducting qubits and enabled the generation, control and characterization of microwave quantum fields. More recently, it was successfully employed to probe the charge dynamics of semiconductor nanostructures at high frequencies. Previous experiments demonstrated a new method to measure the double dot charge stability diagram and characterize the interdot coupling using microwave transmission. In this presentation, we discuss experiments exploring microwave emission from a voltage-biased GaAs double quantum dot. A superconducting coplanar waveguide resonator serves as a tool to study details of the quantum dot level structure that cannot be accessed in transport measurements. We detect radiation emitted in inelastic electron tunneling processes between the dots and the leads and in interdot transitions resonant with the cavity. We will show how the dependence of the emission signal on the quantum dot level configuration provides a novel way to probe the hybridization of the quantum dot states. |
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| Non-linear classical dynamics in a superconducting circuit containing a cavity and a Josephson junction Meister, Selina (Institute for Complex Quantum Systems, Universität Ulm, Germany) |
Motivated by recent experiments [1] a superconducting hybrid circuit consisting of a voltage biased Josephson junction in series with a resonator is studied. For strong driving the dynamics of the system can be very complex, even in the classical regime. Studying the dissipative dynamics within a Langevin-type description, we obtain well-defined dynamical steady states. In contrast to the well-known case of anharmonic potentials, like the Duffing or parametric oscillator, in our case the non-linearity stems from the peculiar way the external drive couples to the system [2]. We investigate the resonance behaviour of this non-linear hybrid system, in particular when driving at higher- or subharmonics. The resulting down- and up-conversions can be observed both, as resonances in the I-V curve, and in the emitted microwave radiation, which yields additional spectral information. [1] M. Hofheinz et al., Bright Side of the Coulomb Blockade, PRL 106, 217005 (2011). [2] V. Gramich et al., From Coulomb-Blockade to Nonlinear Quantum Dynamics in a Superconducting Circuit with a Resonator, PRL 111, 247002 (2013). |
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| Non-equilibrium properties of a microwave resonator coupled to a tunnel junction Mendes, Udson (École Normale Supérieure - Paris, Département de physique, Laboratoire Pierre Aigrain, Paris, France) |
Motivated by the recent advances in the field of mesoscopic circuit quantum electrodynamics, we investigated the effects of a voltage biased tunnel junction coupled with a microwave superconductor resonator. The tunnel junction, which has a linear response to the voltage applied between the two leads, is capacitive coupled with the transmission line. Using Keldysh formalism of non-equilibrium, we obtained the photon effective action and, as a direct consequence of the formalism, we derived the interacting photon Green's function. After that, we calculated the cavity field properties, such as number of photons and second-order correlation function, as a function of voltage applied to the tunnel junction. First, we demonstrated that our formalism recover the well known results obtained via Born-Markov and rotating wave approximations. We then investigated the cavity properties in the limit of voltages smaller or equal to the cavity frequency, where the Born-Markov approximation is not valid. In this limit, non-linear effects are enhanced giving rise to multi-photon processes. |
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For further information please e-mail to: ctcqed15
pks.mpg.de
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