### 63157 results for qubit oscillator frequency

Contributors: Shi, Zhan, Simmons, C. B., Ward, Daniel. R., Prance, J. R., Mohr, R. T., Koh, Teck Seng, Gamble, John King, Wu, Xian., Savage, D. E., Lagally, M. G.

Date: 2012-08-02

low-**frequency** noise processes are an important dephasing mechanism....**Qubit**...**oscillations** visible near δ t = 0 . The **oscillations** of interest appear...**qubit** states varies with external voltages, consistent with a decoherence...**qubit** in a double quantum dot fabricated in a Si/SiGe heterostructure ...**oscillation** **frequency** f for (a–c), respectively. As t is increased, the...**frequency** at more negative detuning (farther from the anti-crossing). ...**oscillation** **frequency** f for the data in (a–c), respectively. We obtain...**oscillations** at a given **frequency** decays with characteristic time T 2 ...**oscillations** of a charge **qubit** in a double quantum dot fabricated in a...**qubit**'s double-well potential). In the regime with the shortest T2*, applying ... Fast quantum **oscillations** of a charge **qubit** in a double quantum dot fabricated in a Si/SiGe heterostructure are demonstrated and characterized experimentally. The measured inhomogeneous dephasing time T2* ranges from 127ps to ~2.1ns; it depends substantially on how the energy difference of the two **qubit** states varies with external voltages, consistent with a decoherence process that is dominated by detuning noise(charge noise that changes the asymmetry of the **qubit**'s double-well potential). In the regime with the shortest T2*, applying a charge-echo pulse sequence increases the measured inhomogeneous decoherence time from 127ps to 760ps, demonstrating that low-**frequency** noise processes are an important dephasing mechanism.

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Contributors: Reuther, Georg M., Hänggi, Peter, Kohler, Sigmund

Date: 2012-05-10

**qubit**-**oscillator** coupling ( g 2 = 0 ), resonant driving, Ω = ω 0 , and...**oscillator** damping γ = 0.02 ϵ . The amplitude A = 0.07 ϵ corresponds to...**oscillator** damping γ . The driving amplitude is A = 3.5 γ , such that ...**qubit**-**oscillator** coupling ( g 1 = 0 ), resonant driving at large **frequency**...**qubit**-**oscillator** Hamiltonian to the dispersive frame and a subsequent ...**qubit** expectation value σ x which exhibits decaying oscillations with ...**qubit** expectation value σ x which exhibits decaying **oscillations** with **frequency** ϵ . The parameters correspond to an intermediate regime between...linear **qubit**-oscillator coupling ( g 2 = 0 ), resonant driving, Ω = ω ...**qubit**-oscillator detuning and by considering also a coupling to the square... **qubit** operator σ x (solid line) and the corresponding purity (dashed)...**qubit** coupled to a resonantly driven dissipative harmonic oscillator. ...**qubit**-oscillator coupling ( g 1 = 0 ), resonant driving at large frequency...**qubit**-**oscillator** master equation in the original frame....**qubit** operator σ x (solid line) and the corresponding purity (dashed) ...**qubit**-oscillator Hamiltonian to the dispersive frame and a subsequent ...**oscillator** damping γ = ϵ , the conditions for the validity of the (Markovian...**qubit** decoherence during dispersive readout...**oscillator** coordinate, which is relevant for flux **qubits**. Analytical results...**qubit** decoherence under generalized dispersive readout, i.e., we investigate...**qubit** coupled to a resonantly driven dissipative harmonic **oscillator**. ...**qubit**-**oscillator** detuning and by considering also a coupling to the square...**qubit**-oscillator master equation in the original frame. ... We study **qubit** decoherence under generalized dispersive readout, i.e., we investigate a **qubit** coupled to a resonantly driven dissipative harmonic **oscillator**. We provide a complete picture by allowing for arbitrarily large **qubit**-**oscillator** detuning and by considering also a coupling to the square of the **oscillator** coordinate, which is relevant for flux **qubits**. Analytical results for the decoherence time are obtained by a transformation of the **qubit**-**oscillator** Hamiltonian to the dispersive frame and a subsequent master equation treatment beyond the Markov limit. We predict a crossover from Markovian decay to a decay with Gaussian shape. Our results are corroborated by the numerical solution of the full **qubit**-**oscillator** master equation in the original frame.

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Contributors: Poletto, S., Chiarello, F., Castellano, M. G., Lisenfeld, J., Lukashenko, A., Cosmelli, C., Torrioli, G., Carelli, P., Ustinov, A. V.

Date: 2008-09-08

**oscillation** **frequency** ω 0 depends on the amplitude of the manipulation...flux **qubit** circuit. (b) The control **flux **Φ c changes the potential barrier...**The** **qubit** is manipulated by changing two magnetic fluxes Φ x and Φ c ,... for **qubit** initialization in **the** left or right well, and Φ x 1 equal to...**the** **qubit** . **The** circuit was manufactured by Hypres using standard Nb/...**the** **qubit** flux is performed by measuring **the** switching current of an unshunted...coherent evolution of **the** **qubit**....**qubits**. An other advantage of this type of **qubit** is its insensitivity ...**oscillation** **frequencies** for the corresponding pulse amplitudes....for **qubit** manipulation at which the **qubit** potential has a shape as indicated...**oscillation** **frequency** could be tuned between 6 and 21 GHz by changing ...**oscillation** **frequencies** for different values of Φ c (open circles). Excellent...**oscillation** **frequency** as shown in Fig. fig:4(a). In Fig. fig:5, we plot...**oscillation** **frequency**, and (b) for different potential symmetry by detuning...**oscillations** of a tunable superconducting flux **qubit** by manipulating its...**qubit** by manipulating its energy potential with a nanosecond-long pulse...**qubit** manipulation at which the **qubit** potential has a shape as indicated...**qubit** circuit. (b) The control flux Φ c changes the potential barrier ...**oscillate** at a **frequency** ranging from 6 GHz to 21 GHz, tunable via the...**qubit** initially prepared in the state, and for (a) different pulse amplitudes...**oscillation** **frequency**, as shown in Fig. fig:4(b), is consistent with ...**qubit** manipulated without microwaves ... We experimentally demonstrate the coherent **oscillations** of a tunable superconducting flux **qubit** by manipulating its energy potential with a nanosecond-long pulse of magnetic flux. The occupation probabilities of two persistent current states **oscillate** at a **frequency** ranging from 6 GHz to 21 GHz, tunable via the amplitude of the flux pulse. The demonstrated operation mode allows to realize quantum gates which take less than 100 ps time and are thus much faster compared to other superconducting **qubits**. An other advantage of this type of **qubit** is its insensitivity to both thermal and magnetic field fluctuations.

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Contributors: Bertet, P., Chiorescu, I., Semba, K., Harmans, C. J. P. M, Mooij, J. E.

Date: 2004-05-03

**frequency** f 2 at the value f 2 * and measured Rabi **oscillations** (black...**oscillations** with high visibility (65%)....**oscillations**....**frequency** to the **qubit** resonance and measured the switching probability...**qubit** by resonant activation...**frequency** of the **qubit** and (insert) persistent-current versus external...**qubit** and (insert) persistent-current versus external flux. The squares...**qubit** damping time T 1 , to prevent loss of excited state population. ...**qubit** state, which we detect by resonant activation. With a measurement...**frequency**. fig4...**oscillations** at a Larmor **frequency** f q = 7.15 ~ G H z (b) Switching probability...high-**frequency** side of the peak. Thus the plasma **oscillator** non-linearity...**qubit** loop (the scale bar indicates 1 ~ μ m ). Two layers of Aluminium...**frequency** on the **qubit** state, which we detect by resonant activation. ...between the **qubit** states in a time shorter than the **qubit**’s energy relaxation...**oscillation** measured by DC current pulse (grey line, amplitude A = 40 ...**qubit**. It relies on the dependency of the measuring Superconducting Quantum...**qubit** to be in 0 would result into broadening of the curve P s w π ), ...**SQUID** and the **qubit** by fitting the **qubit** “step" appearing in the **SQUID** ... We present the implementation of a new scheme to detect the quantum state of a persistent-current **qubit**. It relies on the dependency of the measuring Superconducting Quantum Interference Device (SQUID) plasma **frequency** on the **qubit** state, which we detect by resonant activation. With a measurement pulse of only 5ns, we observed Rabi **oscillations** with high visibility (65%).

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Contributors: Meier, Florian, Loss, Daniel

Date: 2004-08-26

**frequency** is comparable to the coupling energy of micro-circuit and fluctuator...**oscillation** visibility. We also calculate the probability for Bogoliubov...**frequencies**, transitions to the second excited state of the superconducting...single-**frequency** **oscillations** with reduced visibility [Fig. Fig2(b)]....**Qubits**...single-**frequency** **oscillations** are restored. The fluctuator leads to a ...**oscillation** experiments....**oscillations** for a squbit-fluctuator system. The probability p 1 t to ...**oscillations** between quantum states of superconducting micro-circuits ...**frequencies** | b x | / h 100 M H z . We show next that, in this regime, ... Coherent Rabi **oscillations** between quantum states of superconducting micro-circuits have been observed in a number of experiments, albeit with a visibility which is typically much smaller than unity. Here, we show that the coherent coupling to background charge fluctuators [R.W. Simmonds et al., Phys. Rev. Lett. 93, 077003 (2004)] leads to a significantly reduced visibility if the Rabi **frequency** is comparable to the coupling energy of micro-circuit and fluctuator. For larger Rabi **frequencies**, transitions to the second excited state of the superconducting micro-circuit become dominant in suppressing the Rabi **oscillation** visibility. We also calculate the probability for Bogoliubov quasi-particle excitations in typical Rabi **oscillation** experiments.

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Contributors: Makhlin, Yuriy, Shnirman, Alexander

Date: 2003-12-22

**oscillations** of the solid lines are compensated by the dashed line from...low-**frequency**, e.g. 1/f noise, motivated by recent experiments with superconducting...Josephson charge qubit. The simplest Josephson charge qubit is the Cooper-pair...**oscillations** of the solid lines in the diagrams and assuming very slow... ≫ E J for the qubit in Fig. F:qb at the degeneracy point, where the charge...**qubit**. The simplest Josephson charge **qubit** is the Cooper-pair box shown...the qubit’s 2 × 2 density matrix ρ ̂ , exp - i L 0 t θ t , where L 0 is...low-**frequency** noise is equivalent to that of quadratic longitudinal coupling...**frequencies**, we find:...**oscillations** under the influence of both low- and high-**frequency** fluctuations...high-**frequency** dashed line. The relaxation process in e also contributes...**qubit**...the qubit’s density matrix). The term in Fig. F:2ordera gives...**qubits** by transverse low-frequency noise... charge qubit ... We analyze the dissipative dynamics of a two-level quantum system subject to low-**frequency**, e.g. 1/f noise, motivated by recent experiments with superconducting quantum circuits. We show that the effect of transverse linear coupling of the system to low-**frequency** noise is equivalent to that of quadratic longitudinal coupling. We further find the decay law of quantum coherent **oscillations** under the influence of both low- and high-**frequency** fluctuations, in particular, for the case of comparable rates of relaxation and pure dephasing.

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Contributors: Singh, Mandip

Date: 2014-07-01

**flux**-**qubit**-cantilever interrupted by a single Josephson junction is...flux-**qubit**-cantilever corresponds to a quantum entanglement between magnetic...**oscillation** ω i i.e. the **frequency** in absence of magnetic field. The external...**frequency** ( E / h ) is ∼ 4 × 10 11 Hz....**frequency** ( E / h ) is ∼ 3.9 × 10 11 Hz....**oscillator** is introduced that consists of a flux **qubit** in the form of ...**flux** **qubit** with a single Josephson junction is considered throughout this...**oscillates** about an equilibrium angle θ 0 with an intrinsic **frequency** ...flux-**qubit**-cantilever. A part of the flux **qubit** (larger loop) is in the... the **flux**-**qubit**-cantilever to its ground state....**qubit** and the mechanical degrees of freedom of the cantilever are naturally...**oscillation** **frequencies**, consider a flux-**qubit**-cantilever made of niobium...**flux**-**qubit**-cantilever shown in Fig. fig1 where a part of a superconducting...**frequencies** of the flux-**qubit**-cantilever are ω X ≃ 2 π × 7.99 × 10 10 ...**qubit** and the cantilever. An additional magnetic flux threading a DC-SQUID...**qubit** in the form of a cantilever. The magnetic flux linked to the flux...**qubit**...**frequencies** are ω φ ≃ 2 π × 7.99 × 10 10 rad/s, ω δ = 2 π × 22384.5 ...**flux** **qubit** forms a cantilever. The larger loop is interrupted by a smaller ... In this paper a macroscopic quantum **oscillator** is introduced that consists of a flux **qubit** in the form of a cantilever. The magnetic flux linked to the flux **qubit** and the mechanical degrees of freedom of the cantilever are naturally coupled. The coupling is controlled through an external magnetic field. The ground state of the introduced flux-**qubit**-cantilever corresponds to a quantum entanglement between magnetic flux and the cantilever displacement.

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Contributors: Grajcar, M., Izmalkov, A., Il'ichev, E., Wagner, Th., Oukhanski, N., Huebner, U., May, T., Zhilyaev, I., Hoenig, H. E., Greenberg, Ya. S.

Date: 2003-03-31

**frequency** ω T . Then both amplitude v and phase shift χ (with respect...**qubit**, inductively coupled to a Nb LC tank circuit. The resonant properties...**the** **qubit** vs external flux. The dashed lines represent **the** classical potential...probing field to **the** **qubit**, and detects its response....**qubit**, which changes drastically as its flux states pass through degeneracy... **qubit** temperature has been verified [Fig. fig:Temp_dep(b)] to be **the**...**3JJ** **qubit**....** qubit’s** quantum properties, without using spectroscopy. In a range 50 ...

**oscillator**are sensitive to the effective susceptibility (or inductance...

**qubit**anticross [Fig. fig:schem(a)], with a gap of 2 Δ . Increasing ...

**qubit**states. Thus, the tank both applies the probing field to the

**qubit**...

**frequency**due to the change of the effective

**qubit**inductance by the tank...

**the**

**qubit**can adiabatically transform from Ψ l to Ψ r , staying in

**the**...

**qubit**...

**b**) Phase

**qubit**coupled to a tank circuit....

**qubit**vs external flux. The dashed lines represent the classical potential...saturation of

**the**effective

**qubit**temperature at 30 mK. (c) Full dip width...

**qubit**....

**qubit**temperature at 30 mK. (c) Full dip width at half the maximum amplitude...

**qubit**coupled to a tank circuit. ... We have observed signatures of resonant tunneling in an Al three-junction

**qubit**, inductively coupled to a Nb LC tank circuit. The resonant properties of the tank

**oscillator**are sensitive to the effective susceptibility (or inductance) of the

**qubit**, which changes drastically as its flux states pass through degeneracy. The tunneling amplitude is estimated from the data. We find good agreement with the theoretical predictions in the regime of their validity.

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Contributors: Rosenband, Till

Date: 2012-03-01

**oscillator** noise. In this context the squeezed states discussed by Andr...**qubits**, compared to the standard quantum limit (SQL). The most stable ...**qubits**, which are assumed not to decohere with one another....**frequency** corrections are φ E s t / 2 π T . Shaded in the background is...**qubits**, the protocol of Bu...**qubits** performance matches the analytical protocols. In the simulations...**qubits** can reduce clock instability, although the GHZ states yield no...**qubits** are required to improve upon the SQL by a factor of two....15 qubits, and improve upon the SQL variance by a factor of N -1 / 3 ....**oscillator** noise has an Allan deviation of 1 Hz....more qubits, the protocol of Bu...**qubits**, and improve upon the SQL variance by a factor of N -1 / 3 . For...**frequency** variance of the clock extrapolated to 1 second. For long-term...**frequency** is repeatedly corrected, based on projective measurements of...**qubits** yields improved clock stability compared to Ramsey spectroscopy...more qubits can reduce clock instability, although the GHZ states yield...few-**qubit** clock protocols...**oscillator** decoheres due to flicker-**frequency** (1/f) noise. The **oscillator** ... The stability of several clock protocols based on 2 to 20 entangled atoms is evaluated numerically by a simulation that includes the effect of decoherence due to classical **oscillator** noise. In this context the squeezed states discussed by Andr\'{e}, S{\o}rensen and Lukin [PRL 92, 239801 (2004)] offer reduced instability compared to clocks based on Ramsey's protocol with unentangled atoms. When more than 15 atoms are simulated, the protocol of Bu\v{z}ek, Derka and Massar [PRL 82, 2207 (1999)] has lower instability. A large-scale numerical search for optimal clock protocols with two to eight **qubits** yields improved clock stability compared to Ramsey spectroscopy, and for two to three **qubits** performance matches the analytical protocols. In the simulations, a laser local **oscillator** decoheres due to flicker-**frequency** (1/f) noise. The **oscillator** **frequency** is repeatedly corrected, based on projective measurements of the **qubits**, which are assumed not to decohere with one another.

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Contributors: Xia, K., Macovei, M., Evers, J., Keitel, C. H.

Date: 2008-10-14

**qubits** are non-degenerate, and only afterwards render the two **qubits** degenerate...**qubits** via dynamic control of the transition frequencies...**oscillates** at twice the **frequency** of the population **oscillation**, since...**qubit** transition frequencies via the external bias flux in order to maximize...**in **the degenerate two-qubit system of about F = 0.94 is achieved. Finally... flux qubits interacting with each other through their mutual inductance...**qubit** transition **frequencies** around the optimum point. In the figure, ...the two qubits have a frequency difference Δ t = 0 = Δ 0 = 18 γ 0 . Applying...**oscillators**. As our main result, we achieve controlled robust creation...**qubits** interacting with each other through their mutual inductance and...**frequency** Ω 0 = 15 γ 0 and detuning δ = 0 , the symmetric state | s reaches...**frequency** and detuning required for SCRAP....two-**qubit** system....the two qubits are non-degenerate, and only afterwards render the two ...**qubit** transition **frequencies** via the external bias flux in order to maximize...control the qubit transition frequencies around the optimum point. In ...**oscillators**. We present different schemes using continuous-wave control...flux qubits coupled to each other through their mutual inductance M ...The two-qubit Hamiltonian H Q **in **two-level approximation and rotating ...that the two qubits become degenerate, Δ γ 0 t ≥ 160 = 0 . It can be seen...The two qubit transition frequencies are adjusted via time-dependent bias...**oscillate** between | a and | s due to the applied field. This **oscillation**...**oscillations** as a function of δ 0 . The maximum concurrence C is larger...**qubit** transition **frequencies** are adjusted via time-dependent bias fluxes...**qubits** have a **frequency** difference Δ t = 0 = Δ 0 = 18 γ 0 . Applying a...**oscillations** at **frequency** 2 2 Ω 0 , while the amplitude of the subsequent...**qubits** are operated around the optimum point, and decoherence is modelled ... Coherent control and the creation of entangled states are discussed in a system of two superconducting flux **qubits** interacting with each other through their mutual inductance and identically coupling to a reservoir of harmonic **oscillators**. We present different schemes using continuous-wave control fields or Stark-chirped rapid adiabatic passages, both of which rely on a dynamic control of the **qubit** transition **frequencies** via the external bias flux in order to maximize the fidelity of the target states. For comparison, also special area pulse schemes are discussed. The **qubits** are operated around the optimum point, and decoherence is modelled via a bath of harmonic **oscillators**. As our main result, we achieve controlled robust creation of different Bell states consisting of the collective ground and excited state of the two-**qubit** system.

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