Impedance measurement technique for quantum systems

Shevchenko, S. N.

doi:10.1140/epjb/e2008-00061-9

Cited by 17 publications

(18 citation statements)

References 24 publications

(35 reference statements)

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“…2, it relates to the effective inductance of qubits system. The formula obtained for single qubits can be generalized for the two-qubit system [97,142]. Then for the case of low-quality qubits, when their characteristic times are smaller than the tank's period, at the resonance frequency (ξ 0 = 0), expression for the phase shift δ in terms of the parametric inductances L (i) q can be written as following…”

Section: Multi-qubit Systems Equations For a System Of Coupled Qubitsmentioning

confidence: 99%

Multiphoton transitions in Josephson-junction qubits (Review Article)

Shevchenko¹,

Omelyanchouk²,

Il’ichev³

2012

Low Temperature Physics

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Two basic physical models, a two-level system and a harmonic oscillator, are realized on the mesoscopic scale as coupled qubit and resonator. The realistic system includes moreover the electronics for controlling the distance between the qubit energy levels and their populations and to read out the resonator's state, as well as the unavoidable dissipative environment. Such rich system is interesting both for the study of fundamental quantum phenomena on the mesoscopic scale and as a promising system for future electronic devices.We present recent results for the driven superconducting qubit -resonator system, where the resonator can be realized as an LC circuit or a nanomechanical resonator. Most of the results can be described by the semiclassical theory, where a qubit is treated as a quantum two-level system coupled to the classical driving field and the classical resonator. Application of this theory allows to describe many phenomena for the single and two coupled superconducting qubits, among which are the following: the equilibrium-state and weak-driving spectroscopy, Sisyphus damping and amplification, Landau-Zener-Stückelberg interferometry, the multiphoton transitions of both direct and ladder-type character, and creation of the inverse population for lasing. Contents

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Section: Multi-qubit Systems Equations For a System Of Coupled Qubitsmentioning

confidence: 99%

Multiphoton transitions in Josephson-junction qubits (Review Article)

Shevchenko¹,

Omelyanchouk²,

Il’ichev³

2012

Low Temperature Physics

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“…We note that equation (7) describes the series of Lorentzian-shaped multi-photon resonances, while its derivative gives the alternation of positive and negative values. 43 Figure 3a shows the comparison of the measured (left) and calculated (right) LZSM interferometry patterns. Here, we use T 2 = 100 ps, obtained from Fourier analysis, as demonstrated below, and we use T 1 as a fitting parameter.…”

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confidence: 99%

Gate-Sensing Coherent Charge Oscillations in a Silicon Field-Effect Transistor

et al. 2016

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Quantum mechanical effects induced by the miniaturization of complementary metal-oxidesemiconductor (CMOS) technology hamper the performance and scalability prospects of fieldeffect transistors. However, those quantum effects, such as tunnelling and coherence, can be harnessed to use existing CMOS technology for quantum information processing. Here, we report the observation of coherent charge oscillations in a double quantum dot formed in a silicon nanowire transistor detected via its dispersive interaction with a radio-frequency resonant cir- * To whom correspondence should be addressed cuit coupled via the gate. Differential capacitance changes at the inter-dot charge transitions allow us to monitor the state of the system in the strongdriving regime where we observe the emergence of Landau-Zener-Stückelberg-Majorana interference on the phase response of the resonator. A theoretical analysis of the dispersive signal demonstrates that quantum and tunnelling capacitance changes must be included to describe the qubit-resonator interaction. Furthermore, a Fourier analysis of the interference pattern reveals a charge coherence time, T 2 ≈ 100 ps. Our results demonstrate charge coherent control and readout in a simple silicon transistor and open up the possibility to implement charge and spin qubits in existing CMOS technology.1 arXiv:1602.06004v1 [quant-ph]

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“…It turns out that the Sisyphus mechanism of cooling and pumping generates the peakdip structure in the V T ( dc ) curves around the resonance points (see Fig. 7) [23,26]. The point at the V T ( dc ) curves, where transition from dip to peak occurs, corresponds to zero detuning.…”

Section: Ground State Measurementsmentioning

confidence: 95%

“…The degeneracy point of the qubit under strong microwave driving works like an internal beam splitter [28]: the qubit can follow adiabatic (AE'F or CB'D) or Landau-Zener paths (ABC and FED). Therefore, the probability whether the qubit is in the ground or the excited state depends on the interference between all possible paths, which in turn depends on both the energy bias and the amplitude of the microwave driving [26,31]. Since the energy losses of the tank circuit depend on the qubit state, the Landau-Zener interference pattern with Stückelberg oscillations is obtained by scanning the voltage across the tank circuit as a function of the microwave driving amplitude and the energy bias (see Fig.…”

Section: Ground State Measurementsmentioning

confidence: 99%

Weak continuous measurements of multiqubits systems

Il’ichev

Ploeg

Grajcar

et al. 2009

Quantum Inf Process

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In this review we summarize our recent experiments on the investigation on superconducting qubits. Instead of strong projective measurement used by other groups in their first pioneering experiments we have proposed and realized a weak continuous readout which belongs to the class of quantum non-demolition measurements. Moreover, our scheme enables to measure a superconducting qubit at the so called sweet (or magic) point where a qubit is in a superposition of two classical states and its sensitivity to external noise is minimized. In this scheme, which is widely used nowadays, the superconducting oscillator coupled to superconducting qubit is used as a detector of the qubit's state. Such system is analogue to a system of a single atom interacting with photons in a cavity, which allows to study quantum electrodynamics in artificial macroscopic systems. Pushing this analogy we demonstrate Sisyphus cooling and amplification caused by energy exchange between an oscillator and a flux qubit. Using the Sisyphus effect we show consistency between the adiabatic weak continuous measurement in the ground state and the spectroscopic measurement. This allows us to characterize the more complicated system of coupled qubits by making use of the same method. We have realized and studied fixed ferromagnetic, antiferromagnetic as well as tunable qubit-qubit coupling. We argue that ground state measurements can be used for characterization of entangled states in coupled flux qubits. E. Il'ichev (B) · 123 134 E. Il'ichev et al.

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Impedance measurement technique for quantum systems

Cited by 17 publications

References 24 publications

Multiphoton transitions in Josephson-junction qubits (Review Article)

Multiphoton transitions in Josephson-junction qubits (Review Article)

Gate-Sensing Coherent Charge Oscillations in a Silicon Field-Effect Transistor

Weak continuous measurements of multiqubits systems

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