120 research outputs found
Evolution of fragmented states
We consider the problem of evolution of the many-body state of a weakly
interacting system of bosons in an initially fragmented (Fock) state. We show
that the state at any time can be expressed as a continuous superposition of an
infinite number of Gross-Pitaevskii states.Comment: 4 page
Fluorescence interferometry
We describe an interferometer based on fluorescent emission of radiation of
two qubits in quasi-one-dimensional modes. Such a system can be readily
realized with dipole emitters near conducting surface-plasmonic nanowires or
with superconducting qubits coupled to coplanar waveguide transmission lines.Comment: 7 pages, 2 figure
Experimental state control by fast non-Abelian holonomic gates with a superconducting qutrit
Quantum state manipulation with gates based on geometric phases acquired
during cyclic operations promises inherent fault-tolerance and resilience to
local fluctuations in the control parameters. Here we create a general
non-Abelian and non-adiabatic holonomic gate acting in the
subspace of a three-level transmon fabricated in a fully coplanar design.
Experimentally, this is realized by simultaneously coupling the first two
transitions by microwave pulses with amplitudes and phases defined such that
the condition of parallel transport is fulfilled. We demonstrate the creation
of arbitrary superpositions in this subspace by changing the amplitudes of the
pulses and the relative phase between them. We use two-photon pulses acting in
the holonomic subspace to reveal the coherence of the state created by the
geometric gate pulses and to prepare different superposition states. We also
test the action of holonomic NOT and Hadamard gates on superpositions in the
subspace
Cross-coupling effects in circuit-QED stimulated Raman adiabatic passage
Stimulated Raman adiabatic passage is a quantum protocol that can be used for
robust state preparation in a three-level system. It has been commonly employed
in quantum optics, but recently this technique has drawn attention also in
circuit quantum electrodynamics. The protocol relies on two slowly varying
drive pulses that couple the initial and the target state via an intermediate
state, which remains unpopulated. Here we study the detrimental effect of the
parasitic couplings of the drives into transitions other than those required by
the protocol. The effect is most prominent in systems with almost harmonic
energy level structure, such as the transmon. We show that under these
conditions in the presence of decoherence there exists an optimal STIRAP
amplitude for population transfer.Comment: Will be published in proceedings for 28th International Conference
for Low Temperature Physic
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