Search results for "Quantum technology"

Single and two-qubit dynamics in circuit QED architectures

2008

In this paper we overview our researches on the generation and the control of entangled states in the framework of circuit quantum electrodynamics. Applications in the context of quantum computing and quantum information theory are discussed.

Fast Control of Quantum States in Quantum Dots: Limits due to Decoherence

2005

We study the kinetics of confined carrier-phonon system in a quantum dot under fast optical driving and discuss the resulting limitations to fast coherent control over the quantum state in such systems.

Mixed internal-external state approach for quantum computation with neutral atoms on atom chips

2006

We present a realistic proposal for the storage and processing of quantum information with cold Rb atoms on atom chips. The qubit states are stored in hyperfine atomic levels with long coherence time, and two-qubit quantum phase gates are realized using the motional states of the atoms. Two-photon Raman transitions are used to transfer the qubit information from the internal to the external degree of freedom. The quantum phase gate is realized in a double-well potential created by slowly varying dc currents in the atom chip wires. Using realistic values for all experimental parameters (currents, magnetic fields, ...) we obtain high gate fidelities (above 99.9%) in short operation times (~ 1…

Feel the force

2014

An approach based on quantum sensing, in which controlled quantum systems serve as precision sensors, has enabled measurement of the weak magnetic interaction between two electrons bound to two separate ions. See Letter p.376 Every electron carries an intrinsic magnetic dipole moment, so any two electrons should therefore exert magnetic forces on one another. The forces involved are very small, and at atomic scale Coulomb interaction is dominant, so it is extremely difficult to observe the magnetic interaction. However, Shlomi Kotler et al. have now done just that, measuring the interaction between two electrons, in separate trapped strontium-88 ions. The two electrons exhibit spin entangle…

Quantum control theory for decoherence suppression in quantum gates

2007

We show how quantum optimal control theory can help achieve high-fidelity quantum gates in real experimental settings. We discuss several optimization methods (from iterative algorithms to optimization by interference and to impulsive control) and different physical scenarios (from optical lattices to atom chips and to Rydberg atoms).

Hybrid discrete- and continuous-variable quantum information

2015

Research in quantum information processing has followed two different directions: the use of discrete variables (qubits) and that of high-dimensional, continuous-variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful hybrid protocols. The traditional approaches to quantum information processing using either discrete or continuous variables can be combined in hybrid protocols for tasks including quantum teleportation, computation, entanglement distillation or Bell tests.

Protocols and prospects for building a quantum repeater

2013

An overview will be given of various approaches to implementing a quantum repeater for quantum communication over large distances. This includes a discussion of systems and protocols that are experimentally feasible and thus realizable in the midterm in order to go beyond the current limit of a few hundred km given by direct quantum-state transmissions. At the same time, these schemes should be, in principle, scalable to arbitrary distances. In this context, the influence of various elements and strategies in a quantum repeater protocol on the final fidelities and rates shall be addressed: initial entanglement distribution, Bell measurements, multiplexing, postselection, quantum memories, a…

Quantum Computing Experiments with Cold Trapped Ions

2016

Space-Time Symmetries in Quantum Physics

2013

The transformations in space and in time which belong to the Galilei group play an important role in quantum theory. In some respect and for some aspects, their role is new as compared to classical mechanics.

Fundaments of photoelectric readout of spin states in diamond

2021

Abstract The chapter “Fundaments of photoelectric readout of spin states in diamond” deals with the detection of NV centre spins in diamond using the photoelectric detection of magnetic resonances (PDMR) method, introduced in a series of recent publications. It provides in particular insights into the physics of electronic transitions of the NV center, leading to the free carrier generation, and discusses methodologies how to implement the photocurrent detection principles in the dynamically evolving field of quantum technologies. Recent results on the single electron and the single nuclear spin qubits photoelectric readout are presented, along with a microwave-free NV magnetometry techniqu…