Quantum-information processing with circuit quantum electrodynamics

Blais, Alexandre; Gambetta, Jay; Wallraff, Andreas; Schuster, David I.; Girvin, S. M.; Devoret, Michel; Schoelkopf, Robert

doi:10.1103/physreva.75.032329

Cited by 667 publications

(747 citation statements)

References 76 publications

(154 reference statements)

Supporting

Mentioning

735

Contrasting

Unclassified

Order By: Relevance

“…Rather than the slow flux tuning discussed above, we now make use of a strongly detuned rf-drive 23 , which results in an off-resonant Stark shift of the qubit frequencies on the nanosecond time scale. Figure 4a shows the spectroscopy of the two qubits when this off-resonant Stark drive is applied with increasing power.…”

mentioning

confidence: 99%

Coupling superconducting qubits via a cavity bus

Majer

Chow

Gambetta

et al. 2007

Nature

Self Cite

1,293

1,276

View full text Add to dashboard Cite

Superconducting circuits are promising candidates for constructing quantum bits (qubits) in a quantum computer; single-qubit operations are now routine 1,2 , and several examples 3,4,5,6,7,8,9 of two qubit interactions and gates having been demonstrated. These experiments show that two nearby qubits can be readily coupled with local interactions. Performing gates between an arbitrary pair of distant qubits is highly desirable for any quantum computer architecture, but has not yet been demonstrated. An efficient way to achieve this goal is to couple the qubits to a quantum bus, which distributes quantum information among the qubits. Here we show the implementation of such a quantum bus, using microwave photons confined in a transmission line cavity, to couple two superconducting qubits on opposite sides of a chip. The interaction is mediated by the exchange of virtual rather than real photons, avoiding cavity induced loss. Using fast control of the qubits to switch the coupling effectively on and off, we demonstrate coherent transfer of quantum states between the qubits. The cavity is also used to perform multiplexed control and measurement of the qubit states. This approach can be expanded to more than two qubits, and is an attractive architecture for quantum information processing on a chip.There are several physical systems in which one could realize a quantum bus. A particular example is trapped ions 10,11 in which a variety of quantum operations and algorithms have been performed using the quantized motion of the ions (phonons) as the bus. Photons are another natural candidate as a carrier of quantum information 12,13 , because they are highly coherent and can mediate interactions between distant objects. To create a photon bus, it is helpful to utilize the increased interaction strength provided by the techniques of cavity quantum electrodynamics, where an atom is coupled to a single cavity mode. In the strong coupling limit 14 the interaction is coherent, permitting the transfer of quantum information between the atom and the photon. Entanglement between atoms has been demonstrated with Rydberg atom cavity QED 15,16,17 . Circuit QED 18 is a realization of the physics of cavity QED with superconducting qubits coupled to a microwave cavity on a chip. Previous circuit QED experiments with single qubits have achieved 19 the strong coupling limit and have demonstrated 20 the transfer of quantum information from qubit to photon. Here we perform a circuit QED experiment with two qubits strongly coupled to a cavity, and demonstrate a coherent, non-local coupling between the qubits via this bus.Operations with multiple superconducting qubits have been performed and are a subject of current research. The first solid-state quantum gate has been demonstrated with charge qubits 3 . For flux qubits, two-qubit coupling 5 and a controllable coupling mechanism have been realized 7,8,9 . Two phase qubits have also been successfully coupled 4 and the entanglement between them has been observed 6 . All of these interactions h...

show abstract

mentioning

confidence: 99%

Coupling superconducting qubits via a cavity bus

Majer

Chow

Gambetta

et al. 2007

Nature

Self Cite

1,293

1,276

View full text Add to dashboard Cite

show abstract

“…Third, the desirable operation U y1 could be constructed as: U y1 = exp(iπσ y1 /4) = exp(iπσ z1 /4) exp(i3πσ x1 /4) exp(i3πσ z1 /4). It should be pointed out that the durations t x (or t y ) of the single-qubit operations required above for implementing the desirable tomographies is estimated as ∼ 100ps using the experimental parameters: ǫ ∼ 2π ×20MHz [18], and ∆ dr ∼ κ/2 [24]. This is significantly less by at least two orders than the qubit decoherence time, which is measured as ∼ 500ns [24].…”

Section: B Tomographic Reconstruction Of a Single-qubit Statementioning

confidence: 98%

“…So the key to implement the above required operations for tomographies is to realize a two-qubit gate. Again, for the experimental circuit QED system with two superconducting charge qubits, such a gate could be implemented by using the so-called FLICFORQ protocol [24]. In fact, if the cavity is driven by two external fields satisfying the sideband matching condition: ω d2 − ω d1 = Ω 1 + Ω 2 , then an effective Hamiltoniañ…”

Section: (26)mentioning

confidence: 99%

“…It should be pointed out that the durations t x (or t y ) of the single-qubit operations required above for implementing the desirable tomographies is estimated as ∼ 100ps using the experimental parameters: ǫ ∼ 2π ×20MHz [18], and ∆ dr ∼ κ/2 [24]. This is significantly less by at least two orders than the qubit decoherence time, which is measured as ∼ 500ns [24]. Therefore, the required gate operations are accessible and the proposed tomographic reconstructions are experimentally feasible.…”

Section: B Tomographic Reconstruction Of a Single-qubit Statementioning

confidence: 99%

“…Following Ref. [24], under one displacement transformation, the effective Hamiltonian of the resonator plus qubit system can be written as…”

Section: B Tomographic Reconstruction Of a Single-qubit Statementioning

confidence: 99%

See 2 more Smart Citations

High-efficiency tomographic reconstruction of quantum states by quantum nondemolition measurements

Huang¹,

Wei²,

Oh³

2011

Phys. Rev. A

View full text Add to dashboard Cite

We propose a high efficiency tomographic scheme to reconstruct an unknown quantum state of the qubits by using a series of quantum nondemolition (QND) measurements. The proposed QND measurements of the qubits are implemented by probing the the stationary transmissions of the dispersively-coupled resonator. It is shown that only one kind of QND measurements is sufficient to determine all the diagonal elements of the density matrix of the detected quantum state. The remaining non-diagonal elements of the density matrix can be determined by other spectral measurements by beforehand transferring them to the diagonal locations using a series of unitary operations. Compared with the pervious tomographic reconstructions based on the usual destructively projective (DP) measurements (wherein one kind of such measurements could only determine one diagonal element of the density matrix), the present approach exhibits significantly high efficiency for N -qubit (N > 1). Specifically, our generic proposal is demonstrated by the experimental circuit-quantumelectrodynamics (circuit-QED) systems with a few Josephson charge qubits.

show abstract

Bibliography

2022

Principles of Superconducting Quantum Computers

View full text Add to dashboard Cite

Quantum-information processing with circuit quantum electrodynamics

Cited by 667 publications

References 76 publications

Coupling superconducting qubits via a cavity bus

Coupling superconducting qubits via a cavity bus

High-efficiency tomographic reconstruction of quantum states by quantum nondemolition measurements

Bibliography

Contact Info

Product

Resources

About