arXiv subjects

G. Harel

Publications and source records attributed to G. Harel.

9 recordsLinked to original sources

arXiv2005

Coherence protection by the quantum Zeno effect and non-holonomic control in a Rydberg Rubidium isotope

The protection of the coherence of open quantum systems against the influence of their environment is a very topical issue. A scheme is proposed here which protects a general quantum system from the action of a set of arbitrary uncontrolled unitary evolutions. This method draws its inspiration from ideas of standard error-correction (ancilla adding, coding and decoding) and the Quantum Zeno Effect. A pedagogical demonstration of our method on a simple atomic system, namely a Rubidium isotope, is proposed.

quant-ph↗

arXiv2005

Non-Holonomic Control I

In this paper, we present a universal control technique, the non-holonomic control, which allows us to impose any arbitrarily prescribed unitary evolution to any quantum system through the alternate application of two well-chosen perturbations.

quant-ph↗

arXiv2005

Non-holonomic Control II : Non-holonomic Quantum Devices

In this paper, we show how the non-holonomic control technique can be employed to build completely controlled quantum devices. Examples of such controlled structures are provided.

quant-ph↗

arXiv2005

Non-Holonomic Control III : Coherence Protection by the Quantum Zeno Effect and Non-Holonomic Control

In this paper, we present a coherence protection method based upon a multidimensional generalization of the Quantum Zeno Effect, as well as ideas from the coding theory. The non-holonomic control technique is employed as a physical tool which allows its effective implementation. The two limiting cases of small and large quantum systems are considered.

quant-ph↗

arXiv2005

Non-Holonomic Control IV : Coherence Protection in a Rubidium isotope

In this paper, we present a realistic application of the coherence protection method proposed in the previous article. A qubit of information encoded on the two spin states of a Rubidium isotope is protected from the action of electric and magnetic fields.

quant-ph↗

arXiv2005

Implementation of a CNOT gate in two Rydberg atoms by the nonholonomic control technique

We present a demonstrative application of the nonholonomic control method to a real physical system composed of two cold Cesium atoms. In particular, we show how to implement a CNOT quantum gate in this system by means of a controlled Stark field.

quant-ph↗

arXiv2002

Decoherence Correction by the Zeno Effect and Non-Holonomic Control

We show that multidimensional Zeno effect combined with non-holonomic control allows to efficiently protect quantum systems from decoherence by a method similar to classical coding. Contrary to the conventional approach, our method is applicable to arbitrary error-inducing Hamiltonians and general quantum systems. We also propose algorithms of finding encoding that approaches the Hamming upper bound along with methods of practical realizations of the encodings. Two new codes protecting 2 information qubits out of 7 and 4 information qubits out of 9 against a single error with arbitrarily small probability of failure are constructed as an example.

quant-ph↗

arXiv2000

Non-holonomic Quantum Devices

We analyze the possibility and efficiency of non-holonomic control over quantum devices with exponentially large number of Hilbert space dimensions. We show that completely controllable devices of this type can be assembled from elementary units of arbitrary physical nature, and can be employed efficiently for universal quantum computations and simulation of quantum field dynamics.

quant-ph↗

arXiv2000

Recovering Coherence via Conditional Measurements

We show that conditional measurements on atoms following their interaction with a resonant cavity field mode can be used to effectively counter the decoherence of Fock-state superpositions due to cavity leakage.

quant-ph↗