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May 17, 2012

Towards hybrid quantum systems

CORDIS - EU-funded scientists made advances in the development of a hybrid quantum system (HQS) by combining different quantum technologies. The ‘Hybrid quantum systems - integrating atomic/molecular and solid state quantum systems’ (HQS) project combined ultracold atoms with superconducting devices. Scientists considered that an ensemble of ultracold atoms could be coupled to a superconducting transmission line resonator and that the coupling strength could be enhanced by optically excited Rydberg states.

At the experimental level, a dilution refrigerator system was used to measure superconducting resonators which showed quality factors up to a million. In addition, the effect of light impinging on the resonator was tested and provided significant information for systems requiring light pulses.


The Atomchip project has the hybrid quantum system work.

Atom Chips (9 pages) are microfabricated, integrated devices in which electric, magnetic and optical fields can confine, control and manipulate cold atoms. Through miniaturization, atom chips offer a versatile new technology for implementing modern ideas in quantum optics, quantum measurement and quantum information processing. Over the last five years, there has been spectacular progress in preparing and manipulating the quantum states of atom clouds on chips. The next big challenge is manipulating single atoms, allowing them to have controlled collisions and coupling them to single photons in optical microcavities. This emerging technology will lead to new quantum devices and ultimately to quantum information processing on a chip.




Regarding the cryogenic atom chip development, scientists demonstrated strong coupling even at finite temperatures using a 4K resonator. An alternative HQS was developed by coupling a diamond to a superconducting resonator. It was shown that an ensemble of nitrogen-vacancy spins could strongly couple to the superconducting resonator.

The HQS project provided a platform for integrating quantum systems. The developed technology is expected to have a wide variety of applications and bring quantum physics closer to the real world.


Introduction to Atom Chips

Scientific and technological progress in the last decades has shown that miniaturization and integration can lead to robust applications of fundamental physics, be it electronics and semiconductor physics in integrated circuits and data processing, or optics in micro-optical devices, sensors and communication. Atom Chips are starting to realize a similar practical advance for quantum optical systems based on neutral atoms and photons.

In micro electronics, electrons move through micro fabricated wires, switches, transistors, etc. in electronic integrated circuits, chips, to perform elaborate tasks. In Atom Chips, atoms are trapped above a surface, and forces under our control manipulate their motion and internal states. These forces are due to electric, magnetic and optical fields which originate in microscopic structures built on the surface of the chip. The forces produced in this way can confine atoms to micrometer-sized regions, where the characteristic quantum energy h2/2Ma2 (h is Planck’s constant, M is the mass of the atom and a is the 1 μm size of the trap) corresponds to a temperature of a few hundred nanoKelvins. Since the atoms can be much colder than this, quantum effects can be completely dominant, opening the possibility of new quantum devices based on the control of neutral atoms. This quantum confinement idea is precisely the one used to harness the electrons in mesoscopic quantum electronic devices. However, the atoms here are very well isolated from the warm solid state environment, allowing their quantum states to remain undisturbed for tens or hundreds of seconds. The combination of this long decoherence time together with the capability of precise microscopic control makes the atom chip an exceedingly attractive candidate for robust implementation of new quantum devices.

Background

In 2011, Wiley-VCH published a book on atom chips edited by Jakob Reichel and Vladan Vuletic. This group contributed to chapters on atom chip fabrication, interferometry with Bose-Einstein condensates and fermions on atom chips.






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