| 1. |
- Persson, Fredrik, 1978, et al.
(author)
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Excess Dissipation in a Single-Electron Box: The Sisyphus Resistance
- 2010
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:3, s. 953-957
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Journal article (peer-reviewed)abstract
- We present measurements of the ac response of a single-electron box (SEB). We apply a radio frequency signal with a Frequency larger than the tunneling rate and drive the system out of equilibrium. We observe much more dissipation in the SEB then one would expect from a simple circuit model, We can explain this in terms of a mechanism that we call the Sisyphus resistance. The Sisyphus resistance has a strong gate dependence which can be used for electrometery applications.
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| 2. |
- Persson, Fredrik, 1978, et al.
(author)
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Fast readout of a single Cooper-pair box using its quantum capacitance
- 2010
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 82:13, s. Article Number: 134533 -
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Journal article (peer-reviewed)abstract
- We have fabricated a single Cooper-pair box (SCB) together with an on-chip lumped element resonator. By utilizing the quantum capacitance of the SCB, its state can be read out by detecting the phase of a radio-frequency signal reflected off the resonator. The resonator was optimized for fast readout. By studying quasiparticle tunneling events in the SCB, we have characterized the performance of the readout and found that we can perform a single-shot parity measurement, with a signal-to-noise ratio of 1, in approximately 50 ns. This is an order of magnitude faster than previously reported measurements.
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| 3. |
- Sandberg, Martin, 1977, et al.
(author)
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Exploring circuit quantum electrodynamics using a widely tunable superconducting resonator
- 2009
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In: Physica Scripta. - 1402-4896 .- 0031-8949. ; T137, s. Art. no. 014018-
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Journal article (peer-reviewed)abstract
- We have fabricated and characterized systems consisting of superconducting quantum bits (qubits) of the transmon type, coupled to a tunable transmission line resonator. The resonator consists of a superconducting quarter wavelength coplanar waveguide (CPW) resonator that is made tunable by terminating the transmission line to ground through a superconducting quantum interference device (SQUID). Here we present measurements on two devices where we observe Rabi oscillations as we drive the qubit, and vacuum Rabi splitting both as we tune the qubits into resonance with the resonator and as we tune the resonator into resonance with the qubits. We also observe coherent interaction between two resonant qubits. In addition, we demonstrate that we can calculate the response very accurately using a multilevel Hamiltonian.
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| 4. |
- Sandberg, Martin, 1977, et al.
(author)
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Fast tuning of superconducting microwave cavities
- 2008
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In: Proc. 2nd International Workshop on Solid-State Quantum Computing. - 9780735406056 ; , s. 12-21
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Conference paper (peer-reviewed)abstract
- Photons are fundamental excitations of electromagnetic fields and can be captured in cavities. For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific "color". The cavity also has a typical lifetime tau, which results in a finite linewidth delta f. If the size of the cavity is changed fast compared to tau, and so that the frequency change Delta f >> delta f, then it is possible to change the "color" of the captured photons. Here we demonstrate superconducting microwave cavities, with tunable effective lengths. The tuning is obtained by varying a Josephson inductance at one end of the cavity. We show data on four different samples and demonstrate tuning by several hundred linewidths in a time Delta t
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| 5. |
- Sandberg, Martin, 1977, et al.
(author)
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Tuning the field in a microwave resonator faster than the photon lifetime
- 2008
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:20, s. 203501-
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Journal article (peer-reviewed)abstract
- We have fabricated and characterized tunable superconducting transmission line resonators. To change the resonance frequency, we modify the boundary condition at one end of the resonator through the tunable Josephson inductance of a superconducting quantum interference device. We demonstrate a large tuning range (several hundred megahertz), high quality factors (10(4)), and that we can change the frequency of a few-photon field on a time scale orders of magnitude faster than the photon lifetime of the resonator. This demonstration has implications in a variety of applications.
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| 6. |
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| 7. |
- Wilson, Christopher, 1974, et al.
(author)
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Dressed relaxation and dephasing in a strongly driven two-level system
- 2010
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 81:2, s. Art. no. 024520-
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Journal article (peer-reviewed)abstract
- We study relaxation and dephasing in a strongly driven two-level system interacting with its environment. We develop a theory which gives a straightforward physical picture of the complex dynamics of the system in terms of dressed states. In addition to the dressing of the energy diagram, we describe the dressing of relaxation and dephasing. We find a good quantitative agreement between the theoretical calculations and measurements of a superconducting qubit driven by an intense microwave field. The competition of various processes leads to a rich structure in the observed behavior, including signatures of population inversion.
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| 8. |
- Wilson, Christopher, 1974, et al.
(author)
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Photon Generation in an Electromagnetic Cavity with a Time-Dependent Boundary
- 2010
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 105:23, s. 233907-
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Journal article (peer-reviewed)abstract
- We report the observation of photon generation in a microwave cavity with a time-dependent boundary condition. Our system is a microfabricated quarter-wave coplanar waveguide cavity. The electrical length of the cavity is varied using the tunable inductance of a superconducting quantum interference device. It is measured at a temperature significantly less than the resonance frequency. When the length is modulated at approximately twice the static resonance frequency, spontaneous parametric oscillations of the cavity field are observed. Time-resolved measurements of the dynamical state of the cavity show multiple stable states. The behavior is well described by theory. Our results may be considered a preliminary step towards demonstrating the dynamical Casimir effect.
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