Advanced Concepts in Josephson Junction Reflection Amplifiers

Lähteenmäki, Pasi; Vesterinen, Visa; Hassel, Juha; Paraoanu, G. S.; Seppä, Heikki; Hakonen, Pertti

doi:10.1007/s10909-014-1170-0

Cited by 17 publications

(22 citation statements)

References 21 publications

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“…Compared to (30) and (31) they are rather clumsy to use for large K as (100) requires one to compute an n-fold integral for g n−1 (t). However, the integrals only ever involve simple exponentials so they are not too difficult to evaluate for small n. We can at least show that they match the results in (33) and (34).…”

Section: Validity Of the Inverse-number Expansion C1 An Iterative supporting

confidence: 53%

Phase diffusion and the small-noise approximation in linear amplifiers: Limitations and beyond

Chia

Hajdušek

Fazio

et al. 2019

Quantum

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The phase of an optical field inside a linear amplifier is widely known to diffuse with a diffusion coefficient that is inversely proportional to the photon number. The same process occurs in lasers which limits its intrinsic linewidth and makes the phase uncertainty difficult to calculate. The most commonly used simplification is to assume a narrow photon-number distribution for the optical field (which we call the small-noise approximation). For coherent light, this condition is determined by the average photon number. The small-noise approximation relies on (i) the input to have a good signal-to-noise ratio, and (ii) that such a signal-to-noise ratio can be maintained throughout the amplification process. Here we ask: For a coherent input, how many photons must be present in the input to a quantum linear amplifier for the phase noise at the output to be amenable to a small-noise analysis? We address these questions by showing how the phase uncertainty can be obtained without recourse to the small-noise approximation. It is shown that for an ideal linear amplifier (i.e. an amplifier most favourable to the small-noise approximation), the small-noise approximation breaks down with only a few photons on average. Interestingly, when the input strength is increased to tens of photons, the small-noise approximation can be seen to perform much better and the process of phase diffusion permits a small-noise analysis. This demarcates the limit of the small-noise assumption in linear amplifiers as such an assumption is less true for a nonideal amplifier.1 The semiclassical approximation replaces the bosonic annihilation operatorâ by â + δâ and neglects (δâ) 2 and terms with higher order in δâ, where δâ is the deviation ofâ from its average value.Accepted in Quantum 2019-10-09, click title to verify. Published under CC-BY 4.0.

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Section: Validity Of the Inverse-number Expansion C1 An Iterative supporting

confidence: 53%

Phase diffusion and the small-noise approximation in linear amplifiers: Limitations and beyond

Chia

Hajdušek

Fazio

et al. 2019

Quantum

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“…A related development is the recent surge of interest in using similar devices as parametric amplifiers [194]. In this case, the input field is not the vacuum but a real signal that we wish to amplify.…”

Section: Effects Of the Quantum Vacuum And Amplification By Parametrimentioning

confidence: 99%

Quantum systems under frequency modulation

et al. 2017

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Abstract. We review the physical phenomena that arise when quantum mechanical energy levels are modulated in time. The dynamics resulting from changes in the transition frequency is a problem studied since the early days of quantum mechanics. It has been of constant interest both experimentally and theoretically since, with the simple two-state model providing an inexhaustible source of novel concepts. When the transition frequency of a quantum system is modulated, several phenomena can be observed, such as Landau-Zener-Stückelberg-Majorana interference, motional averaging and narrowing, and the formation of dressed states with the presence of sidebands in the spectrum. Adiabatic changes result in the accumulation of geometric phases, which can be used to create topological states. In recent years, an exquisite experimental control in the time domain was gained through the parameters entering the Hamiltonian, and high-fidelity readout schemes allowed the state of the system to be monitored non-destructively. These developments were made in the field of quantum devices, especially in superconducting qubits, as a well as in atomic physics, in particular in ultracold gases. As a result of these advances, it became possible to demonstrate many of the fundamental effects that arise in a quantum system when its transition frequencies are modulated. The purpose of this review is to present some of these developments, from two-state atoms and harmonic oscillators to multilevel and many-particle systems.

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“…In particular, the Josephson junction non-linearity has been recently used for realizing the Josephson parametric amplifier (JPA) [38][39][40][41][42][43] or Josephson traveling-wave parametric amplifier (JTWPA) to generate traveling nonclassical microwave photons in circuit-quantum electrodynamics (circuit-QED) [44,45]. We do not distinguish here between the JPA and JTWPA because both produce a traveling SVS even though they are quite different from each other on other characteristics.…”

Section: Introductionmentioning

confidence: 99%

Implementation of Traveling Odd Schrödinger Cat States in Circuit-QED

2016

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Abstract:We propose a realistic scheme of generating a traveling odd Schrödinger cat state and a generalized entangled coherent state in circuit quantum electrodynamics (circuit-QED). A squeezed vacuum state is used as the initial resource of nonclassical states, which can be created through a Josephson traveling-wave parametric amplifier, and travels through a transmission line. Because a single-photon subtraction from the squeezed vacuum gives an odd Schrödinger cat state with very high fidelity, we consider a specific circuit-QED setup consisting of the Josephson amplifier creating the traveling resource in a line, a beam-splitter coupling two transmission lines, and a single photon detector located at the end of the other line. When a single microwave photon is detected by measuring the excited state of a superconducting qubit in the detector, a heralded cat state is generated with high fidelity in the opposite line. For example, we show that the high fidelity of the outcome with the ideal cat state can be achieved with appropriate squeezing parameters theoretically. As its extended setup, we suggest that generalized entangled coherent states can be also built probabilistically and that they are useful for microwave quantum information processing for error-correctable qudits in circuit-QED.

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Advanced Concepts in Josephson Junction Reflection Amplifiers

Cited by 17 publications

References 21 publications

Phase diffusion and the small-noise approximation in linear amplifiers: Limitations and beyond

Phase diffusion and the small-noise approximation in linear amplifiers: Limitations and beyond

Quantum systems under frequency modulation

Implementation of Traveling Odd Schrödinger Cat States in Circuit-QED

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