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1.
Sci Rep ; 8(1): 10033, 2018 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-29968751

RESUMO

We report development and microwave characterization of rf SQUID (Superconducting QUantum Interference Device) qubits, consisting of an aluminium-based Josephson junction embedded in a superconducting loop patterned from a thin film of TiN with high kinetic inductance. Here we demonstrate that the systems can offer small physical size, high anharmonicity, and small scatter of device parameters. The work constitutes a non-tunable prototype realization of an rf SQUID qubit built on the kinetic inductance of a superconducting nanowire, proposed in Phys. Rev. Lett. 104, 027002 (2010). The hybrid devices can be utilized as tools to shed further light onto the origin of film dissipation and decoherence in phase-slip nanowire qubits, patterned entirely from disordered superconducting films.

2.
Nat Commun ; 7: 12588, 2016 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-27545689

RESUMO

An on-demand single-photon source is a key element in a series of prospective quantum technologies and applications. Here we demonstrate the operation of a tuneable on-demand microwave photon source based on a fully controllable superconducting artificial atom strongly coupled to an open-ended transmission line. The atom emits a photon upon excitation by a short microwave π-pulse applied through a control line. The intrinsically limited device efficiency is estimated to be in the range 65-80% in a wide frequency range from 7.75 to 10.5 GHz continuously tuned by an external magnetic field. The actual demonstrated efficiency is also affected by the excited state preparation, which is about 90% in our experiments. The single-photon generation from the single-photon source is additionally confirmed by anti-bunching in the second-order correlation function. The source may have important applications in quantum communication, quantum information processing and sensing.

3.
Phys Rev Lett ; 115(22): 223603, 2015 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-26650305

RESUMO

A single superconducting artificial atom can be used for coupling electromagnetic fields up to the single-photon level due to an easily achieved strong coupling regime. Bringing a pair of harmonic oscillators into resonance with the transitions of a three-level atom converts atomic spontaneous processes into correlated emission dynamics. We present the experimental demonstration of two-mode correlated emission lasing in harmonic oscillators coupled via a fully controllable three-level superconducting quantum system (artificial atom). The correlation of emissions with two different colors reveals itself as equally narrowed linewidths and quenching of their mutual phase diffusion. The mutual linewidth is more than 4 orders of magnitude narrower than the Schawlow-Townes limit. The interference between the different color lasing fields demonstrates that the two-mode fields are strongly correlated.

4.
Food Sci Technol Int ; 21(4): 284-94, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24831642

RESUMO

Tilapia skin gelatin, pig skin gelatin, and their mousse premixes were exposed to UV irradiation for 103, 206, and 309 kJ/cm(2). All samples after 309 kJ/cm(2) exposure exhibited a significant increase in gel strength, gel forming ability as well as viscosity of solutions. It was shown that UV treatment could also improve the pig skin gelatin foam stability and foam formation ability compared to those of tilapia skin gelatin. Nevertheless, the panelists gave the lowest scores to mousse made with 309 kJ/cm(2) UV-irradiated premix mousse pig skin gelatin. Tilapia skin gelatin could be used as a substitute ingredient for premix mousse made from pig skin gelatin.


Assuntos
Gelatina/química , Pele/química , Suínos , Tilápia , Raios Ultravioleta , Aminoácidos/análise , Animais , Fenômenos Químicos , Emulsificantes/química , Gorduras/química , Alimentos , Gelatina/efeitos da radiação , Géis/química , Proteínas/análise , Sensação , Pele/efeitos da radiação , Soluções/química , Espectroscopia de Infravermelho com Transformada de Fourier , Viscosidade , Água/química
5.
Sci Rep ; 4: 7289, 2014 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-25487352

RESUMO

Three-wave mixing in second-order nonlinear optical processes cannot occur in atomic systems due to the electric-dipole selection rules. In contrast, we demonstrate that second-order nonlinear processes can occur in a superconducting quantum circuit (i.e., a superconducting artificial atom) when the inversion symmetry of the potential energy is broken by simply changing the applied magnetic flux. In particular, we show that difference- and sum-frequencies (and second harmonics) can be generated in the microwave regime in a controllable manner by using a single three-level superconducting flux quantum circuit (SFQC). For our proposed parameters, the frequency tunability of this circuit can be achieved in the range of about 17 GHz for the sum-frequency generation, and around 42 GHz (or 26 GHz) for the difference-frequency generation. Our proposal provides a simple method to generate second-order nonlinear processes within current experimental parameters of SFQCs.

6.
Phys Rev Lett ; 113(6): 063604, 2014 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-25148329

RESUMO

By driving a dispersively coupled qubit-resonator system, we realize an "impedance-matched" Λ system that has two identical radiative decay rates from the top level and interacts with a semi-infinite waveguide. It has been predicted that a photon input from the waveguide deterministically induces a Raman transition in the system and switches its electronic state. We confirm this through microwave response to a continuous probe field, observing near-perfect (99.7%) extinction of the reflection and highly efficient (74%) frequency down-conversion. These proof-of-principle results lead to deterministic quantum gates between material qubits and microwave photons and open the possibility for scalable quantum networks interconnected with waveguide photons.

7.
Nat Commun ; 5: 4480, 2014 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-25059992

RESUMO

The parametric phase-locked oscillator (PPLO) is a class of frequency-conversion device, originally based on a nonlinear element such as a ferrite ring, that served as a fundamental logic element for digital computers more than 50 years ago. Although it has long since been overtaken by the transistor, there have been numerous efforts more recently to realize PPLOs in different physical systems such as optical photons, trapped atoms, and electromechanical resonators. This renewed interest is based not only on the fundamental physics of nonlinear systems, but also on the realization of new, high-performance computing devices with unprecedented capabilities. Here we realize a PPLO with Josephson-junction circuitry and operate it as a sensitive phase detector. Using a PPLO, we demonstrate the demodulation of a weak binary phase-shift keying microwave signal of the order of a femtowatt. We apply PPLO to dispersive readout of a superconducting qubit, and achieved high-fidelity, single-shot and non-destructive readout with Rabi-oscillation contrast exceeding 90%.

8.
Nature ; 484(7394): 355-8, 2012 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-22517162

RESUMO

A hundred years after the discovery of superconductivity, one fundamental prediction of the theory, coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual to the Josephson effect; whereas the latter is a coherent transfer of charges between superconducting leads, the former is a coherent transfer of vortices or fluxes across a superconducting wire. In contrast to previously reported observations of incoherent phase slip, CQPS has been only a subject of theoretical study. Its experimental demonstration is made difficult by quasiparticle dissipation due to gapless excitations in nanowires or in vortex cores. This difficulty might be overcome by using certain strongly disordered superconductors near the superconductor-insulator transition. Here we report direct observation of CQPS in a narrow segment of a superconducting loop made of strongly disordered indium oxide; the effect is made manifest through the superposition of quantum states with different numbers of flux quanta. As with the Josephson effect, our observation should lead to new applications in superconducting electronics and quantum metrology.

9.
Phys Rev Lett ; 107(4): 043604, 2011 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-21867005

RESUMO

We study dynamics of a two-level superconducting quantum system, analogous to a natural atom in an open space, by measuring the evolution of its coherent and incoherent emission. The emitted waves containing full information about the states of the artificial atom are efficiently collected due to strong atom-transmission-line coupling. This allows us to do simultaneous measurements of all the quantum state projections and perform a full characterization of the system. We derive coherence times and extract the two-time correlation function from the dynamics of the coherent emission.

10.
Phys Rev Lett ; 106(21): 217003, 2011 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-21699331

RESUMO

We provide a direct proof of two-electron Andreev transitions in a superconductor-normal-metal tunnel junction by detecting them in a real-time electron counting experiment. Our results are consistent with ballistic Andreev transport with an order of magnitude higher rate than expected for a uniform barrier, suggesting that only part of the interface is effectively contributing to the transport. These findings are quantitatively supported by our direct current measurements in single-electron transistors with similar tunnel barriers.

11.
Phys Rev Lett ; 104(19): 193601, 2010 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-20866963

RESUMO

We present experimental observation of electromagnetically induced transparency (EIT) on a single macroscopic artificial "atom" (superconducting quantum system) coupled to open 1D space of a transmission line. Unlike in an optical media with many atoms, the single-atom EIT in 1D space is revealed in suppression of reflection of electromagnetic waves, rather than absorption. The observed almost 100% modulation of the reflection and transmission of propagating microwaves demonstrates full controllability of individual artificial atoms and a possibility to manipulate the atomic states. The system can be used as a switchable mirror of microwaves and opens a good perspective for its applications in photonic quantum information processing and other fields.

12.
Phys Rev Lett ; 105(2): 026803, 2010 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-20867725

RESUMO

We show that the effect of a high-temperature environment in current transport through a normal metal-insulator-superconductor tunnel junction can be described by an effective density of states in the superconductor. In the limit of a resistive low-Ohmic environment, this density of states reduces into the well-known Dynes form. Our theoretical result is supported by experiments in engineered environments. We apply our findings to improve the performance of a single-electron turnstile, a potential candidate for a metrological current source.

13.
Phys Rev Lett ; 104(18): 183603, 2010 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-20482174

RESUMO

We report amplification of electromagnetic waves by a single artificial atom in open 1D space. Our three-level artificial atom--a superconducting quantum circuit--coupled to a transmission line presents an analog of a natural atom in open space. The system is the most fundamental quantum amplifier whose gain is limited by a spontaneous emission mechanism. The noise performance is determined by the quantum noise revealed in the spectrum of spontaneous emission, also characterized in our experiments.

14.
Science ; 327(5967): 840-3, 2010 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-20150495

RESUMO

An atom in open space can be detected by means of resonant absorption and reemission of electromagnetic waves, known as resonance fluorescence, which is a fundamental phenomenon of quantum optics. We report on the observation of scattering of propagating waves by a single artificial atom. The behavior of the artificial atom, a superconducting macroscopic two-level system, is in a quantitative agreement with the predictions of quantum optics for a pointlike scatterer interacting with the electromagnetic field in one-dimensional open space. The strong atom-field interaction as revealed in a high degree of extinction of propagating waves will allow applications of controllable artificial atoms in quantum optics and photonics.

15.
Phys Rev Lett ; 103(12): 120801, 2009 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-19792419

RESUMO

We demonstrate experimentally that a hybrid single-electron transistor with superconducting leads and a normal-metal island can be refrigerated by an alternating voltage applied to the gate electrode. The simultaneous measurement of the dc current induced by the rf gate through the device at a small bias voltage serves as an in situ thermometer.

16.
Nature ; 449(7162): 588-90, 2007 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-17914393

RESUMO

Solid-state superconducting circuits are versatile systems in which quantum states can be engineered and controlled. Recent progress in this area has opened up exciting possibilities for exploring fundamental physics as well as applications in quantum information technology; in a series of experiments it was shown that such circuits can be exploited to generate quantum optical phenomena, by designing superconducting elements as artificial atoms that are coupled coherently to the photon field of a resonator. Here we demonstrate a lasing effect with a single artificial atom--a Josephson-junction charge qubit--embedded in a superconducting resonator. We make use of one of the properties of solid-state artificial atoms, namely that they are strongly and controllably coupled to the resonator modes. The device is essentially different from existing lasers and masers; one and the same artificial atom excited by current injection produces many photons.

17.
Science ; 316(5825): 723-6, 2007 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-17478714

RESUMO

To do large-scale quantum information processing, it is necessary to control the interactions between individual qubits while retaining quantum coherence. To this end, superconducting circuits allow for a high degree of flexibility. We report on the time-domain tunable coupling of optimally biased superconducting flux qubits. By modulating the nonlinear inductance of an additional coupling element, we parametrically induced a two-qubit transition that was otherwise forbidden. We observed an on/off coupling ratio of 19 and were able to demonstrate a simple quantum protocol.

18.
Phys Rev Lett ; 97(16): 167001, 2006 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-17155426

RESUMO

We have investigated decoherence in Josephson-junction flux qubits. Based on the measurements of decoherence at various bias conditions, we discriminate contributions of different noise sources. We present a Gaussian decay function extracted from the echo signal as evidence of dephasing due to 1/f flux noise whose spectral density is evaluated to be about (10(-6)Phi0)2/Hz at 1 Hz. We also demonstrate that, at an optimal bias condition where the noise sources are well decoupled, the coherence observed in the echo measurement is limited mainly by energy relaxation of the qubit.

19.
Phys Rev Lett ; 97(20): 208901; author reply 208902, 2006 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-17155726
20.
Phys Rev Lett ; 96(13): 137001, 2006 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-16712022

RESUMO

To verify the hypothesis about the common origin of the low-frequency 1/f noise and the quantum f noise recently measured in the Josephson charge qubits, we study the temperature dependence of the 1/f noise and decay of coherent oscillations. The T2 dependence of the 1/f noise is experimentally demonstrated, which supports the hypothesis. We also show that dephasing in the Josephson charge qubits off the electrostatic energy degeneracy point is consistently explained by the same low-frequency 1/f noise that is observed in the transport measurements.

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