### 57622 results for qubit oscillator frequency

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...**qubit**, which changes drastically as its flux states pass through degeneracy...**oscillator** are sensitive to the effective susceptibility (or inductance...**qubit**’s quantum properties, without using spectroscopy. In a range 50 ...**qubit** states. Thus, the tank both applies the probing field to the **qubit**...**qubit** inductance by the tank flux, and (B) losses caused by field-induced...**frequency** due to the change of the effective **qubit** inductance by the tank...**qubit**...**qubit** vs external flux. The dashed lines represent the classical potential...**qubit**....**qubit** temperature at 30 mK. (c) Full dip width at half the maximum amplitude...**qubit** loop is inductively coupled to a parallel resonant tank circuit ...**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: 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: 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: 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: 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: Chiorescu, I., Bertet, P., Semba, K., Nakamura, Y., Harmans, C. J. P. M., Mooij, J. E.

Date: 2004-07-30

**qubit**) junctions have a critical current of 4.2 (0.45) μ A. The device...**oscillator**. We achieve generation and control of the entangled state by...**Qubit** - SQUID device and spectroscopy a, Atomic force micrograph of the...**qubit** - oscillator system for some given bias point. The blue and red ...**qubit** area away from the **qubit** symmetry point. Inset, energy levels of...**frequencies** are shown by the filled squares in b). b, Rabi **frequency**, ...**oscillations**: after a π pulse on the **qubit** resonance ( | 00 → | 10 ) we...**frequencies** indicated by peaks in the SQUID switching probability when...**qubit** - **oscillator** system for some given bias point. The blue and red ...**oscillations** of the coupled system....**oscillations** at the **qubit** symmetry point Δ = 5.9 GHz. a, Switching probability...**qubit** (a two-level system) and a superconducting quantum interference ...**oscillator**, as demonstrated in ion/atom-trap experiments or cavity quantum...**qubit** (the smallest loop closed by three junctions); the **qubit** to SQUID...**qubits**. Single-**qubit** operations, direct coupling between two **qubits**, and...**qubit** coupled to a harmonic oscillator ... In the emerging field of quantum computation and quantum information, superconducting devices are promising candidates for the implementation of solid-state quantum bits or **qubits**. Single-**qubit** operations, direct coupling between two **qubits**, and the realization of a quantum gate have been reported. However, complex manipulation of entangled states - such as the coupling of a two-level system to a quantum harmonic **oscillator**, as demonstrated in ion/atom-trap experiments or cavity quantum electrodynamics - has yet to be achieved for superconducting devices. Here we demonstrate entanglement between a superconducting flux **qubit** (a two-level system) and a superconducting quantum interference device (SQUID). The latter provides the measurement system for detecting the quantum states; it is also an effective inductance that, in parallel with an external shunt capacitance, acts as a harmonic **oscillator**. We achieve generation and control of the entangled state by performing microwave spectroscopy and detecting the resultant Rabi **oscillations** of the coupled system.

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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...**qubit** is measured as a function of Φ x and Φ c fluxes and the switching...**qubits**. An other advantage of this type of **qubit** is its insensitivity ...**oscillation** **frequencies** for the corresponding pulse amplitudes....**qubit** is thus initialized in the chosen potential well. Next, the barrier...**qubit** initialization in the left or right well, and Φ x 1 equal to Φ 0...**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...**qubit** flux state is done by applying a bias current ramp to the dc SQUID...**qubit** by manipulating its energy potential with a nanosecond-long pulse...**oscillations** of a tunable superconducting flux **qubit** by manipulating its...**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**....**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: 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: 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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