Controllable Coherent Population Transfers in Superconducting Qubits for Quantum Computing

Abstract

We propose an approach to coherently transfer populations between selected quantum states in one-and two-qubit systems by using controllable Stark-chirped rapid adiabatic passages (SCRAPs). These evolutiontime insensitive transfers, assisted by easily implementable single-qubit phase-shift operations, could serve as elementary logic gates for quantum computing. Specifically, this proposal could be conveniently demonstrated with existing Josephson phase qubits. Our proposal can find an immediate application in the readout of these qubits. Indeed, the broken parity symmetries of the bound states in these artificial "atoms" provide an efficient approach to design the required adiabatic pulses. PACS number(s): 42.50.Hz, 03.67.Lx, 85.25.Cp.Introduction.-The field of quantum computing is attracting considerable experimental and theoretical attention. Usually, elementary logic gates in quantum computing networks are implemented using precisely designed resonant pulses. The various fluctuations and operational imperfections that exist in practice (e.g., the intensities of the applied pulses and decoherence of the systems), however, limit these designs. For example, the usual π-pulse driving for performing a single-qubit NOT gate requires both a resonance condition and also a precise value of the pulse area. Also, the difficulty of switching on/off interbit couplings [1] strongly limits the precise design of the required pulses for two-qubit gates.

Coherent manipulation of noise-protected superconducting artificial atoms in the Lambda scheme

“…In this work we show how to implement an efficient Λ configuration in these conditions, and we propose a dynamical scheme allowing to operate quantum control. This solves the problem raised in the last decade by several theoretical proposals on the implementation of advanced control by a Λ-scheme in AAs [3,[21][22][23][24][25], which still awaits experimental demonstration.Quantum control via a dynamical Λ scheme is very important because it may provide a fundamental building block for processing in complex architectures. Indeed adiabatic evolution may be used to trigger twophoton absorption-emission pumping cycles, which allow for on demand manipulation of individual photons in distributed quantum networks, as proposed in the cavity-QED realm [26,27].…”

“…In this work we show how to implement an efficient Λ configuration in these conditions, and we propose a dynamical scheme allowing to operate quantum control. This solves the problem raised in the last decade by several theoretical proposals on the implementation of advanced control by a Λ-scheme in AAs [3,[21][22][23][24][25], which still awaits experimental demonstration.…”

“…Demonstrating control by a Λ configuration in last-generation AAs would extend this scenario to the microwave arena, opening the perspective of performing demanding protocols in highly integrated solid-state quantum architectures [13,14], which are usually subject to specific design constraints [28]. Examples are adiabatic holonomic quantum computation [29], information transfer and entanglement generation [24,30,31] between remote nodes, and other sophisticated control protocols [32]. The Λ scheme is described by the standard Hamiltonian in the rotating-wave approximation (RWA), which in a double rotating frame reads [9] H = Ω p 2 |0 2| + Ω s 2 |1 2| + h.c. + δ|1 1| + δ p |2 2| .…”

“…Several works in the last decade [3,[21][22][23][24][25] proposed implementations of Λ-STIRAP in superconducting AAs. However dynamics in the Λ scheme has not yet been experimentally demonstrated for a fundamental reason: protection against low-frequency noise [6] necessary to achieve large decoherence times is attained by operating the device by a Hamiltonian with exact or approximate symmetries [5,37].…”

Simultaneous control of optical dipole force and coherence creation by super-Gaussian femtosecond pulses inΛ-like atomic systems

“…Today, coherent control techniques are widely used in the fields of robust quantum dot excitation generation [18], controllable coherent population transfer in superconducting qubits [19], atomic interferometry [20,21], high precession spectroscopy [22,23], quantum computing [24,25], quantum information processing [26,27], ultrafast optical switching [28][29][30] and population transfer in four level atoms [31]. In the last two or three decades or so, many efficient schemes such as stimulated Raman adiabatic passage (STIRAP), Raman chirped adiabatic passage (RCAP) and adiabatic rapid passage (ARP) for controlling the population transfer between the quantum states of atoms and molecules has opened new routes for controlling the various atomic and molecular processes [1,2,[32][33][34].…”