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Quantum Physics: Disentangling Strange Behavior Of Qubits

Date:
August 8, 2008
Source:
Basque Research
Summary:
Current technology enables the building of electrical circuits similar to those we use at home but reduced thousands of times in size to a micrometric scale of thousandths of a millimeter. When these circuits are built of superconductor materials and at near-absolute zero cryogenic temperatures, the world of everyday physics is left behind and the amazing world of quantum physics is entered. In this circuit the behavior is something like an artificial atom (i.e. like the so-called quantum bits ("qubits") of quantum computers) and the concepts of quantum optics, quantum information and condensed matter are mixed.

Current technology enables the building of electrical circuits similar to those we use at home but reduced thousands of times in size to a micrometric scale of thousandths of a millimetre. When these circuits are built of superconductor materials and at near-absolute zero cryogenic temperatures, the world of everyday physics is left behind and the amazing world of quantum physics is entered.

In this circuit the behaviour is something like an artificial atom (i.e. like the so-called quantum bits (“qubits”) of quantum computers) and the concepts of quantum optics, quantum information and condensed matter are mixed.

An Ikerbasque researcher, ascribed to the University of the Basque Country (UPV/EHU), Enrique Solano, together with colleagues from Germany and Japan, have been working on an experiment and a theoretical model that show that certain quantum leaps are prohibited at times between levels of a qubit superconductor.

This phenomenon is produced on sending photons of light with sufficient energy against a qubit installed within a circuit that simulates the behaviour of microwaves, similar to the ovens commonly used domestically but at a micrometric scale.

To explain this in an easy way, consider a household circuit where, as with any such circuit, sufficient energy has to be supplied in order to move electrons from one place to another, i.e. the required voltage has to be applied.

In an atomic circuit, however, the required energy is supplied through photons of light but this is not sufficient to produce the famous quantum jumps between two atomic energy levels. The additional required factor is the presence of the symmetry of the qubit, an enhancing factor, as it were. It is as if it were not enough for the quantum nature to have the required energy and it requires, moreover, the presence of the qubit to enable – or otherwise – the quantum leaps stimulated by the photons of light energy.

If the qubit presents itself with symmetrical potential, the jump is prohibited and is not produced; curiously, if the potential is asymmetric, the quantum leap is permitted. This strange behaviour has been demonstrated by these researchers both at a theoretical level and in the laboratory, where the rules of prohibition may be activated and deactivated at will.

This research is an important step in the thorough understanding of the quantum jumps permitted and prohibited in superconductor circuits, as well as in the potential application of the electrodynamic quantum of circuits to future technology in quantum computation and information.

Enrique Solano is a PhD in Physics from the Federal University of Río de Janeiro. After working at the Ludwig-Maximilian University in Munich, he has been carrying out his research over the last few months at the UPV/EHU.


Story Source:

The above story is based on materials provided by Basque Research. Note: Materials may be edited for content and length.


Journal Reference:

  1. Deppe et al. Two-photon probe of the Jaynes–Cummings model and controlled symmetry breaking in circuit QED. Nature Physics, 2008; DOI: 10.1038/nphys1016

Cite This Page:

Basque Research. "Quantum Physics: Disentangling Strange Behavior Of Qubits." ScienceDaily. ScienceDaily, 8 August 2008. <www.sciencedaily.com/releases/2008/07/080725093454.htm>.
Basque Research. (2008, August 8). Quantum Physics: Disentangling Strange Behavior Of Qubits. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2008/07/080725093454.htm
Basque Research. "Quantum Physics: Disentangling Strange Behavior Of Qubits." ScienceDaily. www.sciencedaily.com/releases/2008/07/080725093454.htm (accessed April 20, 2014).

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