Search results for "Coherence time"
showing 6 items of 16 documents
Magnons at low excitations: Observation of incoherent coupling to a bath of two-level systems
2019
Collective magnetic excitation modes, magnons, can be coherently coupled to microwave photons in the single excitation limit. This allows for access to quantum properties of magnons and opens up a range of applications in quantum information processing, with the intrinsic magnon linewidth representing the coherence time of a quantum resonator. Our measurement system consists of a yttrium iron garnet (YIG) sphere and a three-dimensional (3D) microwave cavity at temperatures and excitation powers typical for superconducting quantum circuit experiments. We perform spectroscopic measurements to determine the limiting factor of magnon coherence at these experimental conditions. Using the input-o…
Quantum gate in the decoherence-free subspace of trapped ion qubits
2009
We propose a geometric phase gate in a decoherence-free subspace with trapped ions. The quantum information is encoded in the Zeeman sublevels of the ground-state and two physical qubits to make up one logical qubit with ultra long coherence time. Single- and two-qubit operations together with the transport and splitting of linear ion crystals allow for a robust and decoherence-free scalable quantum processor. For the ease of the phase gate realization we employ one Raman laser field on four ions simultaneously, i.e. no tight focus for addressing. The decoherence-free subspace is left neither during gate operations nor during the transport of quantum information.
Temporal phase control of bound-bound and bound-free two-photon transitions in NO with two time-delayed cross-polarized pulses
2001
0953-4075; Temporal phase control over the multi-photoionization of NO is investigated experimentally The coherent excitation of the molecular system is achieved by a sequence of two phase-related non-Fourier-transform-limited laser pulses delivered by a nanosecond dye laser, The phase-locked pulses are produced by making use of an actively stabilized interferometer with a tunable pathlength difference. As the coherence time of the laser is comparable with the inhomogenous dephasing time of the medium, the measurements are performed with temporally overlapped pulses. In order to avoid the modulation of the ionic signal coming from optical interference, the linear polarizations of the two pu…
On the observability of parity and time reversal violating interactions by trapped ion spectroscopy
1982
The feasibility to measure neutral weak current interactions by spectroscopy on trapped ions is investigated. The sensitivity of the proposed experiment is compared to the sensitivity of similar experiments using atomic gases or beams. It is shown that there is no advantage as far as that part of the interaction is concerned which is a vector in the nucleon current and an axial vector in the electron current. This is mainly due to the relatively low ion density. The circular polarization however depending upon the nuclear spin orientation appears to be proportional to the coherence time, which is three orders of magnitude longer than in ordinary atomic beam resonance experiments. It is poin…
Memory-assisted long-distance phase-matching quantum key distribution
2019
We propose a scheme that generalizes the loss scaling properties of twin-field or phase-matching quantum key distribution (QKD) related to a channel of transmission $\eta_{total}$ from $\sqrt{\eta_{total}}$ to $\sqrt[2n]{\eta_{total}}$ by employing n-1 memory stations with spin qubits and n beam-splitter stations including optical detectors. Our scheme's resource states are similar to the coherent-state-based light-matter entangled states of a previous hybrid quantum repeater, but unlike the latter our scheme avoids the necessity of employing 2n-1 memory stations and writing the transmitted optical states into the matter memory qubits. The full scaling advantage of this memory-assisted phas…
Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission
2019
AbstractWe report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.