Robust atomic quantum information processing networks in periodic lattice structures
The main scientific objective of this project is the development of schemes for scalable and robust quantum computing in
periodic lattice structures which are feasible with current or short-term experimental technology. We plan to achieve this by
using decoherence free subspaces in ensembles of atoms stored in periodic traps and examine methods for performing robust single and two qubit gates in these subspaces. We study implementations based on strong atomic interactions (e.g. controllable molecular interactions) and on flexible interactions mediated by a cavity field. These schemes are extended to
quantum networks and checked for their suitability for implementation in concrete experimental setups. Such proposals have become realistic due to recent experimental breakthroughs in manipulating and controlling atoms in optical lattices and the networks we investigate should allow to build special purpose quantum computers which can be used e.g. for small
specific tasks in quantum cryptography or for simulations of more complicated quantum systems.
| Investigators: | U. Dorner and D. Jaksch
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| Acronym: | RAQUIN
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| Funded by: | EU Marie Curie Intra European Fellowship; Call: FP6-2002-Mobility-5; Contract No. MEIF-CT-2004-010796
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| Start date: | 2004-12-01
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| End date: | 2006-11-30
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Related Publications
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U. Dorner, A. Klein and D. Jaksch,
A quantum repeater based on decoherence free subspaces,
Quant. Inf. Comp. 8, 0468 (2008).
We study a quantum repeater which is based on decoherence free quantum gates recently proposed by Klein et al. [Phys. Rev. A, 73, 012332 (2006)]. A number of operations on the decoherence free subspace in this scheme makes use of an ancilla qubit which undergoes dephasing and thus introduces decoherence to the system. We examine how this decoherence affects entanglement swapping and purification as well as the performance of a quantum repeater. We compare the decoherence free quantum repeater with a quantum repeater based on qubits that are subject to decoherence and show that it outperforms the latter when decoherence due to long waiting times of conventional qubits becomes significant. Thus, a quantum repeater based on decoherence free subspaces is a possibility to greatly improve quantum communication over long or even intercontinental distances.
created: 01-06-2007, last modified: 17-04-2008
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A. Klein, U. Dorner, C. Moura Alves and D. Jaksch,
Robust implementations of Quantum Repeaters,
Phys. Rev. A 73, 012332 (2006).
We show how to efficiently exploit decoherence free subspaces,
which are immune to collective noise, for realizing quantum
repeaters with long lived quantum memories. Our setup consists of an
assembly of simple modules and we show how to implement them in
systems of cold, neutral atoms in arrays of dipole traps. We develop
methods for realizing robust gate operations on qubits encoded in a
DFS using collisional interactions between the atoms. We also give a
detailed analysis of the performance and stability of all required
gate operations and emphasize that all modules can be realized with
current or near future experimental technology.
created: 08-11-2005, last modified: 24-01-2006
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U. Dorner, T. Calarco, P. Zoller, A. Browaeys and P. Grangier,
Quantum logic via optimal control in holographic dipole traps,
J. Opt. B 7, 341 (2005).
We propose a scheme for quantum logic with neutral atoms stored in an array of holographic dipole traps where the positions of the atoms can be rearranged by using holographic optical tweezers. In particular, this allows for the transport of two atoms to the same well where an external control field is used to perform gate operations via the molecular interaction between the atoms. We show that optimal control techniques allow for the fast implementation of the gates with high fidelity.
created: 08-09-2005, last modified: 11-01-2006
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W.H. Zurek, U. Dorner and P. Zoller,
Dynamics of a Quantum Phase Transition,
Phys. Rev. Lett. 95, 105701 (2005).
We present two approaches to the dynamics of a quench-induced phase transition in the quantum Ising model. One follows the standard treatment of thermodynamic second order phase transitions but applies it to the quantum phase transitions. The other approach is quantum, and uses Landau-Zener formula for transition probabilities in avoided level crossings. We show that predictions of the two approaches of how the density of defects scales with the quench rate are compatible, and discuss the ensuing insights into the dynamics of quantum phase transitions.
created: 08-09-2005