Quantum detection at millimeter wavelengths

Tucker, J. R.; Feldman, M.J.

doi:10.1103/revmodphys.57.1055

Cited by 728 publications

(447 citation statements)

References 116 publications

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“…If we start from the unpumped dc IVC, t ͑v dc ͒, and apply a high- frequency signal, so the total voltage across the junction is v͑t͒ = v dc + v ac cos͑ t + ͒, then, according to Ref. 24, the total dc quasiparticle tunneling current pump of the pumped junction will be given by…”

Section: Including the Self-pumping Effectmentioning

confidence: 99%

Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

et al. 2007

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We have numerically investigated the dynamics of a long linear Josephson tunnel junction with overlap geometry. Biased by a direct current ͑dc͒ and an applied dc magnetic field, the junction has important applications as tunable high frequency oscillator ͓flux-flow oscillator ͑FFO͔͒ in the millimeter and submillimeter range. The study is performed in the frame of a modified sine-Gordon model, which includes surface losses, self-pumping effect, and in an empirical way the superconducting gap. The electromagnetic coupling to the environment is modeled by a simple resistor-capacitor load ͑RC load͒ placed at both ends of the FFO. In our model, the damping parameter depends both on the spatial coordinate and on the amplitude of the ac voltage. In order to find the dc current-voltage curves, the damping parameter has to be calculated self-consistently by successive approximations and time integration of the perturbed sine-Gordon equation. The modified model gives better qualitative agreement with experimental results than the conventional perturbed sine-Gordon model.

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Section: Including the Self-pumping Effectmentioning

confidence: 99%

Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

et al. 2007

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“…The SIS quasiparticle tunnel junction mixer has been shown to have great potential for producing heterodyne receivers with noise performances approaching the quantum limit [1]. The results discussed here were achieved by using a 0.36/zm 2 Nb/AlOx/Nb tunnel junction in a full height rectangular wavegnide mixer [21 with two circular noncontacting tuning elements [3,4] and an integrated 1-2 GI-Iz wide IF matching network.…”

Section: Introductionmentioning

confidence: 99%

A lownoise 665 GHz SIS quasi-particle waveguide receiver

Kooi

Walker

Leduc

et al. 1994

Int J Infrared Milli Waves

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We report recent results on a 565-690 GHz SIS heterodyne receiver employing a 0.36pro 2 Nb/AlOx/Nb SIS tunnel junction with high quality circular non-contacting backshort and E-plane tuners in a full height waveguide mount. No resonant tuning structures have been incorporated in the junction design at this time, even though such structures are expected to help the performance of the receiver. The receiver operates to at least the gap frequency of Niobium, _-, 680 GHz. Typical receiver noise temperatures from 565-690 GI-Iz range from 160K to 230K with a best value of 185K DSB at 648 GHz. With the mixer cooled from 4.3K to 2K the measured receiver noise temperatures decreased by approximately 15%, giving roughly 180K DSB from 660 to 680 GHz. The receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii.

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“…The left inequality of Eq. (1) is known as the condition for the quantum regime of absorption [11,[27][28][29], and by analogy we call this regime of depairing the "quantum regime of depairing." The right inequality of Eq.…”

mentioning

confidence: 99%

Coherent Excited States in Superconductors due to a Microwave Field

et al. 2016

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We describe theoretically the depairing effect of a microwave field on diffusive s-wave superconductors. The ground state of the superconductor is altered qualitatively in analogy to the depairing due to a dc current. In contrast to dc depairing, the density of states acquires, for microwaves with frequency ω 0 , steps at multiples of the photon energy Δ AE nℏω 0 and shows an exponential-like tail in the subgap regime. We show that this ac depairing explains the measured frequency shift of a superconducting resonator with microwave power at low temperatures. DOI: 10.1103/PhysRevLett.117.047002 How is the superconducting state modified by a current, i.e., when the condensate is moving? The answer to this question is well known for the case of a dc current flowing in a superconducting wire. For a dc current, the Cooper pairs gain a finite momentum which leads to the suppression of the superconducting properties of the wire [1,2]. The modulus of the superconducting order parameter Δ is reduced and the sharp BCS singularity near the gap is smeared. This depairing effect of a current or of a magnetic field was studied theoretically soon after the creation of the microscopic theory of superconductivity [3]. The moving superconducting condensate has been called a coherent excited state generated by the momentum displacement operator ρ q ¼ P n expðiq · r n Þ by Anderson [4] as part of the explanation of the Meissner effect from the original form of the BCS theory. The momentum displacement operator, when applied to the BCS ground state, creates excited pairs of electrons k 1 , k 2 with the momentum pairing k 1 þ k 2 ¼ q instead of zero [1,[4][5][6]. This momentum displacement q ¼ jqj corresponds to a superfluid drift velocity v s ¼ ℏq=m, where m is the electron mass. In the Green's function technique, it is possible to introduce the superfluid velocity in a gauge-invariant way, v s ∝ ½∇φ − ð2e=ℏÞA , where φ is the phase of the superconductor, e the electron charge, and A the vector potential of the electromagnetic field. The equivalence of depairing due to an electric current and due to a magnetic field is well established, both theoretically [7] and experimentally [2], using thin and narrow superconducting wires with a uniform current density. The theory of depairing by a dc current was reformulated, using the Usadel equations [8], for diffusive films with an elastic scattering length much smaller than the BCS coherence length [9]. The results of this theory [9] were confirmed experimentally by Romijn et al. However, a general theory for depairing by a microwave field, a time-dependent vector potential A, has not been formulated. In current experimental research, there are many cases in which a superconductor is used at very low temperatures, T=T c ≪ 1, where the density of quasiparticles is very low and the response of the superconductor is dominated by the response of the superfluid. At higher temperatures, it is well known that microwave radiation can be absorbed by quasiparticles, leading to a nonequilibrium di...

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Quantum detection at millimeter wavelengths

Cited by 728 publications

References 116 publications

Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

A lownoise 665 GHz SIS quasi-particle waveguide receiver

Coherent Excited States in Superconductors due to a Microwave Field

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