### 57529 results for qubit oscillator frequency

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...**qubits** interacting with each other through their mutual inductance M and...**oscillates** at twice the **frequency** of the population **oscillation**, since...**qubit** transition frequencies via the external bias flux in order to maximize...**qubit** transition **frequencies** around the optimum point. In the figure, ...**oscillators**. As our main result, we achieve controlled robust creation...**qubits** interacting with each other through their mutual inductance and...**qubit** transition frequencies around the optimum point. In the figure, ...**frequency** Ω 0 = 15 γ 0 and detuning δ = 0 , the symmetric state | s reaches...**frequency** and detuning required for SCRAP....two-**qubit** system....**qubit** transition **frequencies** via the external bias flux in order to maximize...**qubits** have a frequency difference Δ t = 0 = Δ 0 = 18 γ 0 . Applying a...**qubit** transition frequencies are adjusted via time-dependent bias fluxes...**oscillators**. We present different schemes using continuous-wave control...two-**qubit** system of about F = 0.94 is achieved. Finally, the TDMF is switched...**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...flux **qubits** coupled to each other through their mutual inductance M ...**qubit** transition **frequencies** are adjusted via time-dependent bias fluxes...two-**qubit** Hamiltonian H Q in two-level approximation and rotating wave...**qubits** have a **frequency** difference Δ t = 0 = Δ 0 = 18 γ 0 . Applying a...**qubits** become degenerate, Δ γ 0 t ≥ 160 = 0 . It can be seen from Fig....**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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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**...**qubit** in a double quantum dot fabricated in a Si/SiGe heterostructure ...**qubit** states varies with external voltages, consistent with a decoherence...**oscillations** visible near δ t = 0 . The **oscillations** of interest appear...**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: Saito, Keiji, Wubs, Martijn, Kohler, Sigmund, Hanggi, Peter, Kayanuma, Yosuke

Date: 2006-03-07

**qubit**-oscillator states for a coupling strength γ = 0.6 ℏ v and oscillator...**qubit**, being independent of the frequency of the QED mode. Possible applications...**qubit** and the **oscillator**, and can be written as...**frequencies** Ω . The dashed line marks the Ω -independent, final probability...**frequency** Ω = 0.5 v / ℏ ....**oscillator** **frequency**, P ↑ ↓ t resembles the standard LZ transition with...**qubit**-oscillator coupling γ are determined by the design of the setup,...**frequency** Ω and the **qubit**-**oscillator** coupling γ are determined by the ...**qubit**, being independent of the **frequency** of the QED mode. Possible applications...**qubit**-**oscillator** entanglement....**qubit** comes into resonance with the oscillator sometime during the sweep...**qubit**-**oscillator** states for a coupling strength γ = 0.6 ℏ v and **oscillator**...**qubit** comes into resonance with the **oscillator** sometime during the sweep...**qubit** undergoing Landau-Zener transitions enabled by the coupling to a...**oscillator** **frequency** Ω , despite the fact that this is not the case for... **qubit** flip, the resulting dynamics is restricted to the states | ↑ , ... **qubit** is in state | ↓ is depicted in Fig. fig:one-osc. It demonstrates...**qubit**-oscillator entanglement....**oscillations** that are typical for the tail of a LZ transition are averaged... **qubit** and the oscillator, and can be written as ... We study a **qubit** undergoing Landau-Zener transitions enabled by the coupling to a circuit-QED mode. Summing an infinite-order perturbation series, we determine the exact nonadiabatic transition probability for the **qubit**, being independent of the **frequency** of the QED mode. Possible applications are single-photon generation and the controllable creation of **qubit**-**oscillator** entanglement.

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Contributors: Oxtoby, Neil P., Gambetta, Jay, Wiseman, H. M.

Date: 2007-06-24

**qubit**, is used to damp a classical oscillator circuit. The resulting realistic...**frequency** (rf) weak measurements where a low-transparency quantum point...low-**frequency** (dc) weak measurements. In this paper we extend realistic...**oscillator** circuit to be a QPC (see Fig. fig:dqdqpc for details). Measurement...**qubit**. A schematic of the isolated DQD and capacitively coupled QPC is...**qubit**. The charge basis states are denoted | 0 and | 1 (see Fig. fig:...**qubit** electron, denoted by E 1 and E 0 for the near and far dot, respectively...**qubit** coupled to a classical L C oscillator with inductance L and capacitance...**qubits** is important for quantum computation, particularly for the purposes...**qubit** coupled to a classical L C **oscillator** with inductance L and capacitance...radio-**frequency** point contact), with two benefits over the SET — lower...**qubit** using a radio-frequency quantum point contact including experimental...**frequency** is the same as the signal of interest (or very slightly detuned...**qubit**. The rf+dc mode of operation is considered. Here the QPC is biased...**qubit**, is used to damp a classical **oscillator** circuit. The resulting realistic...low-**frequency** beats due to mixing the signal with the LO are easily detected...charge-**qubit** detector, that may nevertheless be higher than the dc-QPC...**qubit** and capacitively coupled low-transparency QPC between source (S)...**oscillator**, L O , and then measured. fig:rfcircuit...**oscillator** (relative to the QPC), where the **oscillator** slaves to the **qubit** ... The extension of quantum trajectory theory to incorporate realistic imperfections in the measurement of solid-state **qubits** is important for quantum computation, particularly for the purposes of state preparation and error-correction as well as for readout of computations. Previously this has been achieved for low-**frequency** (dc) weak measurements. In this paper we extend realistic quantum trajectory theory to include radio **frequency** (rf) weak measurements where a low-transparency quantum point contact (QPC), coupled to a charge **qubit**, is used to damp a classical **oscillator** circuit. The resulting realistic quantum trajectory equation must be solved numerically. We present an analytical result for the limit of large dissipation within the **oscillator** (relative to the QPC), where the **oscillator** slaves to the **qubit**. The rf+dc mode of operation is considered. Here the QPC is biased (dc) as well as subjected to a small-amplitude sinusoidal carrier signal (rf). The rf+dc QPC is shown to be a low-efficiency charge-**qubit** detector, that may nevertheless be higher than the dc-QPC (which is subject to 1/f noise).

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Contributors: Higgins, Kieran D. B., Lovett, Brendon W., Gauger, Erik M.

Date: 2012-03-27

**qubit** dynamics. We obtain a new expression for the ac Stark shift and ...**qubit** dynamics are not greatly perturbed by the presence of the oscillator...**qubit** design but with an **oscillating** voltage applied to the CPB bias gate...**qubit** dynamics in this regime, based on an oscillator correlation function...**oscillations** are also shown as a reference (green). Left: the population...**qubit**. These parameters can be achieved experimentally using the same **qubit** design but with an oscillating voltage applied to the CPB bias gate...**oscillator** Hilbert space at a point where the dynamics have converged ...**frequency** of the **qubit** dynamics is still adequately captured by our single...**qubit** dynamics is still adequately captured by our single term approximation...**qubit** and **oscillator**, thus requiring a theoretical treatment beyond the...**qubit** dynamics analytically unwieldy, because the rational function form...**qubit** and oscillator, thus requiring a theoretical treatment beyond the...**qubit** **frequency** Ω with temperature. The upper inset shows the dependence...**qubit** frequency Ω with temperature. The upper inset shows the dependence...**oscillator** on the **qubit**. These parameters can be achieved experimentally...**qubit** thermometry of an oscillator....**oscillator** represents a ubiquitous physical system. New experiments in...**frequency** domain. The full numerical solution was Fourier transformed ...**qubit** dynamics are not greatly perturbed by the presence of the **oscillator**...**qubit** dynamics in this regime, based on an **oscillator** correlation function...**qubit** thermometry: T i n is the temperature supplied to the numerical ...**oscillations** with **frequency** ( eqn:rho3) to it. The blue line is the data...**qubit** thermometry of an **oscillator**. ... A quantum two level system coupled to a harmonic **oscillator** represents a ubiquitous physical system. New experiments in circuit QED and nano-electromechanical systems (NEMS) achieve unprecedented coupling strength at large detuning between **qubit** and **oscillator**, thus requiring a theoretical treatment beyond the Jaynes Cummings model. Here we present a new method for describing the **qubit** dynamics in this regime, based on an **oscillator** correlation function expansion of a non-Markovian master equation in the polaron frame. Our technique yields a new numerical method as well as a succinct approximate expression for the **qubit** dynamics. We obtain a new expression for the ac Stark shift and show that this enables practical and precise **qubit** thermometry of an **oscillator**.

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Contributors: Liberti, G., Zaffino, R. L., Piperno, F., Plastina, F.

Date: 2005-11-21

**qubit** is coupled to a single oscillator mode....**qubit** is coupled to a single **oscillator** mode. 99 weiss U. Weiss, Quantum...**frequency** and the level asymmetry of the **qubit**. This is done in the adiabatic...**qubit**. This is done in the adiabatic regime in which the time evolution...**oscillator** in the lower adiabatic potential, for D = 10 and α = 2 and ...**qubit** is much faster than the oscillator one. Within the adiabatic approximation...**oscillator** defined in Eq. ( due1), centered in Q = ± Q 0 , respectively...**qubit** ( W = D = 0 ) would have given a pair of independent parabolas instead...**qubit** strongly interacting with an oscillator mode, as a function of the...**qubit** tunnelling amplitude D . One can appreciate that the result of Eq...**qubit** with an ohmic environment was numerically analyzed. It turns out...**qubit** is coupled to a single **oscillator** mode....**qubit** coupled to a resonator in the adiabatic regime...**qubit** and the environmental **oscillator**. Unfortunately, the coupling strength...**qubit** is much faster than the **oscillator** one. Within the adiabatic approximation...**qubit** strongly interacting with an **oscillator** mode, as a function of the...**qubit** Hamiltonian. As mentioned in section sect2 above, this is due to ... We discuss the ground state entanglement of a bi-partite system, composed by a **qubit** strongly interacting with an **oscillator** mode, as a function of the coupling strenght, the transition **frequency** and the level asymmetry of the **qubit**. This is done in the adiabatic regime in which the time evolution of the **qubit** is much faster than the **oscillator** one. Within the adiabatic approximation, we obtain a complete characterization of the ground state properties of the system and of its entanglement content.

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Contributors: Lisenfeld, Juergen, Mueller, Clemens, Cole, Jared H., Bushev, Pavel, Lukashenko, Alexander, Shnirman, Alexander, Ustinov, Alexey V.

Date: 2009-09-18

**qubit**. (As the anharmonicity Δ / h ∼ 100 MHz in our circuit is relatively...**frequency** while the **qubit** was kept detuned. A π pulse was applied to measure...**frequencies**. Each trace was recorded after adjusting the **qubit** bias to...**qubit**-fluctuator system...**oscillations**
...**qubits** often show signatures of coherent coupling to microscopic two-level...**qubit**’s Rabi frequency Ω q / h is set to 48 MHz....**frequencies** in the rotating frame correspond to the **frequencies** of the...**frequency** of 7.805 GHz (indicated by a dashed line)....**qubits**, Josephson junctions, two-level
fluctuators, microwave spectroscopy...**qubit** and fluctuator v ⊥ and to the microwave field Ω q and Ω f v ....**qubit** levels....**qubit** in the excited state, P t , vs. driving **frequency**; (b) Fourier-transform...**qubit**, in which we induce Rabi oscillations by resonant microwave driving...** qubit’s** Rabi

**frequency**Ω q / h is set to 48 MHz....

**oscillations**observed experimentally....

**frequency**, revealing the coupling to a two-level defect state having a...

**qubit**in the excited state, P t , vs. driving frequency; (b) Fourier-transform...

**qubit**loop. The

**qubit**state is controlled by an externally applied microwave...

**qubit**circuit (the

**qubit**subspace) and disregard the longitudinal coupling...

**qubit**, in which we induce Rabi

**oscillations**by resonant microwave driving...

**qubit**is tuned close to the resonance with an individual TLF and the Rabi...

**qubit**relative to the TLF’s resonance

**frequency**, which is indicated in...

**qubit**above or below the fluctuator's level-splitting. Theoretical analysis...

**qubit**circuit. (b) Probability to measure the excited

**qubit**state (color-coded...

**qubit**-TLF coupling), interesting 4-level dynamics are observed. The experimental...

**frequency**of order of the

**qubit**-TLF coupling), interesting 4-level dynamics...

**qubit**’s excited state....

**qubit**transition. In this work, we studied the

**qubit**interacting with...

**qubit**. ... Superconducting

**qubits**often show signatures of coherent coupling to microscopic two-level fluctuators (TLFs), which manifest themselves as avoided level crossings in spectroscopic data. In this work we study a phase

**qubit**, in which we induce Rabi

**oscillations**by resonant microwave driving. When the

**qubit**is tuned close to the resonance with an individual TLF and the Rabi driving is strong enough (Rabi

**frequency**of order of the

**qubit**-TLF coupling), interesting 4-level dynamics are observed. The experimental data shows a clear asymmetry between biasing the

**qubit**above or below the fluctuator's level-splitting. Theoretical analysis indicates that this asymmetry is due to an effective coupling of the TLF to the external microwave field induced by the higher

**qubit**levels.

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Contributors: unknown

**qubit**–oscillator coupling γ. Parameters: γ=0.25ℏv and ℏΩ2=100ℏv, as before...**qubit** may undergo Landau–Zener transitions due to its coupling to one ...**qubit**–oscillator entanglement, with state-of-the-art circuit QED as a ...**qubit** are well suited for the robust creation of entangled cavity states...**qubit** that is coupled to one **oscillator**. Starting in the ground state ...**qubit** coupled to one **oscillator**, far outside the RWA regime: γ=ℏΩ=0.25ℏv...**qubit** coupled to two oscillators with degenerate energies. Parameters:...**qubit** coupled to two cavities, we show that Landau–Zener sweeps of the...**qubit** coupled to two oscillators. Parameters: γ=0.25ℏv, ℏΩ1=90ℏv, and ...**oscillator** **frequencies**, both inside and outside the regime where a rotating-wave...**qubit** coupled to two **oscillators**. Parameters: γ=0.25ℏv, ℏΩ1=90ℏv, and ...**oscillators**. We show that for a **qubit** coupled to one **oscillator**, Landau–Zener...**qubit** coupled to one oscillator, Landau–Zener transitions can be used ...**qubit** coupled to two oscillators with large energies, and with detunings...**qubit** would be measured |↑〉....**oscillator** if the **qubit** would be measured in state |↓〉; the dash-dotted...**qubit** coupled to two **oscillators** with degenerate energies. Parameters:...**qubit**–**oscillator** entanglement, with state-of-the-art circuit QED as a ... A **qubit** may undergo Landau–Zener transitions due to its coupling to one or several quantum harmonic **oscillators**. We show that for a **qubit** coupled to one **oscillator**, Landau–Zener transitions can be used for single-photon generation and for the controllable creation of **qubit**–**oscillator** entanglement, with state-of-the-art circuit QED as a promising realization. Moreover, for a **qubit** coupled to two cavities, we show that Landau–Zener sweeps of the **qubit** are well suited for the robust creation of entangled cavity states, in particular symmetric Bell states, with the **qubit** acting as the entanglement mediator. At the heart of our proposals lies the calculation of the exact Landau–Zener transition probability for the **qubit**, by summing all orders of the corresponding series in time-dependent perturbation theory. This transition probability emerges to be independent of the **oscillator** **frequencies**, both inside and outside the regime where a rotating-wave approximation is valid.

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Contributors: Wubs, Martijn, Kohler, Sigmund, Hanggi, Peter

Date: 2007-03-15

**qubit** coupled to two oscillators. Parameters: γ = 0.25 ℏ v , ℏ Ω 1 = 90...**qubit** that is coupled to one oscillator. Starting in the ground state ...**qubit**-oscillator couplings γ 1 = γ 2 = γ . Still, the frequency detuning...**qubit**-**oscillator** coupling γ . Parameters: γ = 0.25 ℏ v and ℏ Ω 2 = 100...**qubit**. In general not much can be said about this final state, but let...**oscillator** depend on the state of the **qubit**....**qubit** coupled to two cavities, we show that Landau-Zener sweeps of the...**oscillator** **frequency**. In Fig. fig:photon_averages we depict how for a...**qubit** coupled to two **oscillators**. Parameters: γ = 0.25 ℏ v and Ω 2 = 100...**qubit**-**oscillator** coupling, then the dynamics can very well be approximated...**qubit**-oscillator entanglement, with state-of-the-art circuit QED as a ...**oscillator** if the **qubit** would be measured in state | ↓ ; the dash-dotted...**qubit**-**oscillator** entanglement, with state-of-the-art circuit QED as a ...**oscillator** energies ℏ Ω 1 , 2 are much larger than the **qubit**-**oscillator**...**qubit** coupled to two oscillators. Parameters: γ = 0.25 ℏ v and Ω 2 = 100...**qubit** are well suited for the robust creation of entangled cavity states...**qubit** coupled to one **oscillator**, far outside the RWA regime: γ = ℏ Ω =...**qubit** state is | ↑ . We call this dynamical selection rule the “no-go-up...**qubit** coupled to two oscillators with degenerate energies. Parameters:...**qubit** may undergo Landau-Zener transitions due to its coupling to one ...**qubit**-oscillator coupling γ . Parameters: γ = 0.25 ℏ v and ℏ Ω 2 = 100...**oscillator** **frequencies**, both inside and outside the regime where a rotating-wave...**qubit** coupled to two **oscillators**. Parameters: γ = 0.25 ℏ v , ℏ Ω 1 = 90...**oscillators**. We show that for a **qubit** coupled to one **oscillator**, Landau-Zener...**qubit** would be measured | ↑ . fig:photon_averages...**qubit** coupled to one oscillator, Landau-Zener transitions can be used ...**qubit**....**qubit** coupled to two **oscillators** with degenerate energies. Parameters: ... A **qubit** may undergo Landau-Zener transitions due to its coupling to one or several quantum harmonic **oscillators**. We show that for a **qubit** coupled to one **oscillator**, Landau-Zener transitions can be used for single-photon generation and for the controllable creation of **qubit**-**oscillator** entanglement, with state-of-the-art circuit QED as a promising realization. Moreover, for a **qubit** coupled to two cavities, we show that Landau-Zener sweeps of the **qubit** are well suited for the robust creation of entangled cavity states, in particular symmetric Bell states, with the **qubit** acting as the entanglement mediator. At the heart of our proposals lies the calculation of the exact Landau-Zener transition probability for the **qubit**, by summing all orders of the corresponding series in time-dependent perturbation theory. This transition probability emerges to be independent of the **oscillator** **frequencies**, both inside and outside the regime where a rotating-wave approximation is valid.

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Contributors: Makhlin, Yuriy, Shnirman, Alexander

Date: 2003-12-22

**qubit**’s density matrix). The term in Fig. F:2ordera gives...**oscillations** of the solid lines are compensated by the dashed line from...**qubit**’s 2 × 2 density matrix ρ ̂ , exp - i L 0 t θ t , where L 0 is the...low-**frequency**, e.g. 1/f noise, motivated by recent experiments with superconducting...**oscillations** of the solid lines in the diagrams and assuming very slow...**frequency** domain, one constrains the **frequency** of the dashed line to be...**qubit** in Fig. F:qb at the degeneracy point, where the charge noise is ...**qubit**. The simplest Josephson charge **qubit** is the Cooper-pair box shown...low-**frequency** noise is equivalent to that of quadratic longitudinal coupling...**oscillations** under the influence of both low- and high-**frequency** fluctuations...high-**frequency** dashed line. The relaxation process in e also contributes...**qubit**...**qubits** by transverse low-frequency noise ... 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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