Continuous Monitoring of Rabi Oscillations in a Josephson Flux Qubit

Il’ichev, E.; Oukhanski, N.; Izmalkov, A.; Wagner, Th.; Grajcar, M.; Meyer, H.‐G.; Smirnov, Anatoly Yu.; Brink, Alec Maassen van den; Amin, M. H. S.; Zagoskin, A. M.

doi:10.1103/physrevlett.91.097906

Cited by 145 publications

(137 citation statements)

References 19 publications

Supporting

Mentioning

133

Contrasting

Order By: Relevance

“…More recently superconducting qubits were shown to act as artificial two-level atoms, displaying Rabi oscillations, Ramsey fringes, and further quantum effects 1,2,3 . Coupling such qubits to resonators 4,5,6,7 brought the superconducting circuits into the realm of quantum electrodynamics (circuit QED). It opened the perspective to use superconducting qubits as micro-coolers or to create a population inversion in the qubit to induce lasing behavior of the resonator 8,9,10,11 .…”

mentioning

confidence: 99%

Sisyphus cooling and amplification by a superconducting qubit

et al. 2008

Self Cite

View full text Add to dashboard Cite

Laser cooling of the atomic motion paved the way for remarkable achievements in the fields of quantum optics and atomic physics, including Bose-Einstein condensation and the trapping of atoms in optical lattices. More recently superconducting qubits were shown to act as artificial two-level atoms, displaying Rabi oscillations, Ramsey fringes, and further quantum effects 1,2,3 . Coupling such qubits to resonators 4,5,6,7 brought the superconducting circuits into the realm of quantum electrodynamics (circuit QED). It opened the perspective to use superconducting qubits as micro-coolers or to create a population inversion in the qubit to induce lasing behavior of the resonator 8,9,10,11 . Furthering these analogies between quantum optical and superconducting systems we demonstrate here Sisyphus cooling 12 of a low frequency LC oscillator coupled to a near-resonantly driven superconducting qubit. In the quantum optics setup the mechanical degrees of freedom of an atom are cooled by laser driving the atom's electronic degrees of freedom. Here the roles of the two degrees of freedom are played by the LC circuit and the qubit's levels, respectively. We also demonstrate the counterpart of the Sisyphus cooling, namely Sisyphus amplification.For red-detuned high-frequency driving of the qubit the low-frequency LC circuit performs work in the forward and backward part of the oscillation cycle, always pushing the qubit up in energy, similar to Sisyphus who always had to roll a stone uphill. The oscillation cycle is completed with a relaxation process, when the work performed by the oscillator together with a quantum of energy of the high-frequency driving is released by the qubit to the environment via spontaneous emission. For blue-detuning the same mechanism creates excitations in the LC circuit with a tendency towards lasing and the characteristic line-width narrowing. In this regime "lucky Sisyphus" always rolls the stone downhill. Parallel to the experimental demonstration we analyze the system theoretically and find quantitative agreement, which supports the interpretation and allows us to estimate system parameters.The system considered is shown in the inset of Fig. 1. It consists of a three-junction flux qubit 13 , with the two qubit FIG. 1: (a) The energy levels of the qubit as a function of the energy bias of the qubit ε(fx) = 2Φ0Ipfx. The sinusoidal current in the tank coil, indicated by the wavy line, drives the bias of the qubit. The starting point of the cooling (heating) cycles is denoted by blue (red) dots. The resonant excitation of the qubit due to the high-frequency driving, characterized by ΩR0, is indicated by two green arrows and by the Lorentzian depicting the width of this resonance. The relaxation of the qubit is denoted by the black dashed arrows. The inset shows a schematic of the qubit coupled to an LC circuit. The high frequency driving is provided by an on-chip microwave antenna. (b) SEM picture of the superconducting flux qubit prepared by shadow evaporation technique.

show abstract

mentioning

confidence: 99%

Sisyphus cooling and amplification by a superconducting qubit

et al. 2008

Self Cite

View full text Add to dashboard Cite

show abstract

“…[12][13][14] With regard to using superconducting systems in quantum technologies, it has been shown that Josephson weak link circuits, and in particular SQUID rings in the quantum regime, are highly nonperturbative in nature and can generate very strong nonlinear interactions with classical circuit environments. [15][16][17][18] In this paper we provided a demonstration that this nonperturbative ͑nonlinear͒ behavior is crucial to the understanding of the interaction of SQUID rings with circuit environments. In this work we first consider the adiabatic ͑ground state͒ interaction of a quantum regime SQUID ring inductively coupled to a classical parallel resonance LC ͑tank͒ circuit.…”

Section: Introductionmentioning

confidence: 99%

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

et al. 2005

View full text Add to dashboard Cite

We consider the interaction of a quantum mechanical SQUID ring with a classical resonator ͑a parallel LC tank circuit͒. In our model we assume that the evolution of the ring maintains its quantum mechanical nature, even though the circuit to which it is coupled is treated classically. We show that when the SQUID ring is driven by a classical monochromatic microwave source, energy can be transferred between this input and the tank circuit, even when the frequency ratio between them is very large. Essentially, these calculations deal with the coupling between a single macroscopic quantum object ͑the SQUID ring͒ and a classical circuit measurement device where due account is taken of the nonperturbative behavior of the ring and the concomitant nonlinear interaction of the ring with this device.

show abstract

“…The measurement record in such a situation is a fluctuating current I(t) that accumulates a distinguishable signal-to-noise ratio after some time. 17,18 On one hand, the weak coupling between detector and qubit(s) permits the quantum system to remain relatively well isolated from "outside" classical noise. On the other hand, it means that instead of simple abrupt collapse, 19 we have to deal with a theory of continuous (weak) mea-surements of a single quantum system.…”

Section: Introductionmentioning

confidence: 99%

Quantum Zeno stabilization in weak continuous measurement of two qubits

Ruskov

Korotkov²,

Mizel³

2006

Phys. Rev. B

View full text Add to dashboard Cite

We have studied quantum coherent oscillations of two qubits under continuous measurement by a symmetrically coupled mesoscopic detector. The analysis is based on a Bayesian formalism that is applicable to individual quantum systems. Measurement continuously collapses the two-qubit system to one of the sub-spaces of the Bell basis. For a detector with linear response this corresponds to measurement of the total spin of the qubits. In the other extreme of purely quadratic response the operator σ 1 y σ 2 y + σ 1 z σ 2 z is measured. In both cases, collapse naturally leads to spontaneous entanglement which can be identified by measurement of the power spectrum and/or the average current of the detector. Asymmetry between the two qubits results in evolution between the different measurement subspaces. However, when the qubits are even weakly coupled to the detector, a kind of quantum Zeno effect cancels the gradual evolution and replaces it with rare, abrupt switching events. We obtain the asymptotic switching rates for these events and confirm them with numerical simulations. We show how such switching affects the observable power spectrum on different time scales.

show abstract

Continuous Monitoring of Rabi Oscillations in a Josephson Flux Qubit

Cited by 145 publications

References 19 publications

Sisyphus cooling and amplification by a superconducting qubit

Sisyphus cooling and amplification by a superconducting qubit

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

Quantum Zeno stabilization in weak continuous measurement of two qubits

Contact Info

Product

Resources

About