Coherent manipulation of superconducting quantum interference devices with adiabatic passage

Abstract

The method of stimulated Raman adiabatic passage is applied in order to coherently manipulate a three-level superconducting quantum interference device quantum bit with two microwave pulses. Simulations indicate that this method has the potential to allow for efficient control of the system for a wide range of pulse parameters. IntroductionIn the quest for practical systems for carrying out quantum computations [1], solid-state systems that make use of the Josephson effect are viable candidates [2]. This has been exhibited in a series of important experiments [3][4][5][6][7][8][9][10][11][12][13][14]. One particular scheme is based on magnetic flux states in superconducting quantum interference devices (SQUIDs) [2,[15][16][17][18][19][20][21][22][23][24][25][26]. In some of these schemes [2,[16][17][18][19], the SQUID quantum bit, or qubit, which is the basic element of a SQUID quantum computer, is based on a two-level system manipulated by external fields. The interaction of these systems with both classical [2,16,17] and quantized [18,19] fields has been analysed.Zhou et al.[20] have recently proposed a three-level Ã-type rf-SQUID qubit. Here, the states of the qubit are the two lower flux states j0i and j1i of the à system, and the manipulation of the qubit is done with two microwave fields that couple the lower states to an upper state jei. As the transition matrix elements corresponding to the transitions j0i $ jei and j1i $ jei are larger than that of the j0i $ j1i transition, the three-level SQUID qubit has been shown to be more favourable than the conventional two-level SQUID qubit for implementing a NOT gate. Amin et al. [21] have shown that the scheme of Zhou et al. is incomplete and have proposed an improved scheme for the rotation of a three-level SQUID qubit. More recently, Yang and Han [22] have addressed the same problem using far-off-resonant Raman coupling to achieve an arbitrary rotation of a three-level SQUID qubit. They have demonstrated that large detunings of the driving fields from the upper state could be favourable for

Quantum left-handed metamaterial from superconducting quantum-interference devices

“…For n = 4, x 04 = 5.39798 × 10 −3 , which is given by Ref. [11,12]. Taking L = 100pH, we obtain α = 11.815GHz.…”

Controlled Decoherence of Three-level Floating Qubit

“…For an extremely high temperature, furthermore, setting T φ → ∞, there is T 2 = 2T 1 . Differently from the gate speed, the decoherent time will reduce with increasing of coupling matrix elements [22]. Fortunately, one may extend the decoherent time to the regime of three-level structure by controlling the external circuit.…”

“…As an example, the decoherent times are calculated in a realistic SQUID system with the same parameters as Paspalakis et al's [22], where L = 10 2 pH, C = 40 fF, and I C = 3.95 µA. Thus, the values of the two lowest energies and auxiliary level |4 of the system are ω 0 = 7.81984 meV, ω 2 = 8.00136 meV, ω 4 = 8.14057 meV so that the matrix elements are x 02 = 0.0323051, x 40 = 0.00539798, x 42 = 0.0428826.…”

Measuring the quality factor of a microwave cavity using superconducting qubit devices

“…Several theoretical proposals have analyzed the interaction between SC qubits and quantized [1,6,7,8,9,10,11] or classical fields [12,13,14]. The strong coupling of a single photon to a SC charge qubit has been experimentally demonstrated [15] by using a one-dimensional transmission line resonator [16].…”