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- Rochus Klesse
- 2008

We work out a theory of approximate quantum error correction that allows us to derive a general lower bound for the entanglement fidelity of a quantum code. The lower bound is given in terms of Kraus operators of the quantum noise. This result is then used to analyze the average error correcting performance of codes that are randomly drawn from unitarily… (More)

- Rochus Klesse, Sandra Frank
- Physical review letters
- 2005

We consider quantum error correction of quantum noise that is created by a local interaction of qubits with a common bosonic bath. The possible exchange of bath bosons between qubits gives rise to spatial and temporal correlations in the noise. We find that these kinds of noise correlations have a strong negative impact on quantum error correction.

- Rochus Klesse
- Open Syst. Inform. Dynam.
- 2008

We present a proof for the quantum channel coding theorem which relies on the fact that a randomly chosen code space typically is highly suitable for quantum error correction. In this sense, the proof is close to Shannon’s original treatment of information transmission via a noisy classical channel. 1 Preliminaries 1.1 Quantum channel In the theory of… (More)

- R Klesse, M R Zirnbauer
- Physical review letters
- 2001

We formulate and prove an exact relation which expresses the moments of the two-point conductance for an open disordered electron system in terms of certain density correlators of the corresponding closed system. As an application of the relation, we demonstrate that the typical two-point conductance for the Chalker-Coddington model at criticality… (More)

- Stephan Kleinbölting, Rochus Klesse
- Physical review. E, Statistical, nonlinear, and…
- 2015

We consider thermalization of a microscopic quantum system by interaction with a thermal bath. Our interest is the minimal size the bath can have while still being able to thermalize the system. Within a specific thermalization scheme, we show that a single spin 1/2 can be fully thermalized by interaction with a bath that consists of just two other spins… (More)

The superiority of quantum computation over conventional computation relies on the fact that a quantumbit (qubit) register can be in the superposition of a very large number of classical computational states. At the same time, maintaining coherence of this highly superpositional state poses also the main obstacle for the realization of a quantum computer.… (More)

- Thomas Zell, Friedemann Queisser, Rochus Klesse
- Physical review letters
- 2009

Within a generalized Caldeira-Leggett model, we analyze the conditions under which a bosonic heat bath can entangle two microscopic quantum systems at a distance r. We find that the attainable entanglement is extremely distance-sensitive. Significant entanglement can only be achieved if the systems are within a microscopic distance that is of order of the… (More)

- Rochus Klesse
- 2008

We review the time evolution of wavepackets at the metal-insulator transition in twoand three-dimensional disordered systems. The importance of scale invariance and multifractal eigenfunction fluctuations is stressed. The implications of the frequencyand wavevector-dependence of the diffusion coefficient are compared with the results of numerical… (More)

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