### 63094 results for qubit oscillator frequency

Contributors: Martijn Wubs, Sigmund Kohler, Peter Hänggi

Date: 2007-10-01

**qubit** may undergo Landau–Zener transitions due to its coupling to one ...a qubit coupled to two oscillators. Parameters: γ=0.25ℏv and Ω2=100ℏv,...**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 cavities, we show that Landau–Zener sweeps of the...**oscillator** **frequencies**, both inside and outside the regime where a rotating-wave...**qubit** coupled to two **oscillators**. Parameters: γ=0.25ℏv, ℏΩ1=90ℏv, and ...case** the **qubit would be measured |↑〉.
...**oscillators**. We show that for a **qubit** coupled to one **oscillator**, Landau–Zener... the qubit–oscillator coupling γ. Parameters: γ=0.25ℏv and ℏΩ2=100ℏv, ...**qubit** coupled to one oscillator, Landau–Zener transitions can be used ...**oscillator** if the **qubit** would be measured in state |↓〉; the dash-dotted...**qubit** coupled to two **oscillators** with degenerate energies. Parameters:...**sweep** of a qubit coupled to two oscillators with degenerate energies. ...**qubit**–**oscillator** entanglement, with state-of-the-art circuit QED as a ...LZ **sweep** of a qubit coupled to two oscillators. Parameters: γ=0.25ℏv, ... 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: 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: 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: 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: Chiorescu, I., Bertet, P., Semba, K., Nakamura, Y., Harmans, C. J. P. M., Mooij, J. E.

Date: 2004-07-30

**oscillator**. We achieve generation and control of the entangled state by...**frequencies** are shown by the filled squares in b). b, Rabi **frequency**, .......**oscillations**: after a π pulse on the **qubit** resonance ( | 00 → | 10 ) we...flux **qubit** (the smallest loop closed by three junctions); the **qubit** to...**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** symmetry point Δ = 5.9 GHz. a, Switching probability as a function...**oscillator**, as demonstrated in ion/atom-trap experiments or cavity quantum...**qubit** (a two-level system) and a superconducting quantum interference ...**qubits**. Single-**qubit** operations, direct coupling between two **qubits**, and... the **qubit** transition. In the upper scan, the system is first excited ...through the **qubit** area away from the **qubit** symmetry point. Inset, energy...**qubit** coupled to a harmonic oscillator...Qub ... 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: 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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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: 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: 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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