Details of Grant 

EPSRC Reference:	GR/T09088/01
Title:	Electronic Surface States & Qubits on Liquid Helium
Principal Investigator:	Lea, Professor MJ
Other Investigators:	Antonov, Professor V
Researcher Co-Investigators:	Dr PH Glasson
Project Partners:	University of Bristol
Department:	Physics
Organisation:	Royal Holloway, Univ of London
Scheme:	Standard Research (Pre-FEC)
Starts:	01 June 2004	Ends:	29 February 2008	Value (£):	529,143
EPSRC Research Topic Classifications:	Quantum Fluids & Solids
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
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Summary on Grant Application Form
While conventional computers are based on the manipulation of bits (0 or 1), Quantum Information Processing (QIP) requires the manipulation of quantum systems, which can exist in two possible quantum states (qubits). The power of QIP hinges on the fact that a system can also exist in a linear combination of these states. The physical realisation of a simple quantum computer with the potential to be scaled to a larger device is exciting a lot of research internationally.We propose to study the quantum states of an electron, trapped above superfluid liquid helium, as potential qubits, and construct a simple quantum computer with an array of such electrons. The quantum states of each electron, arising from motion perpendicular to the surface, are like a one dimensional hydrogen atom. The ground state and first excited state form the qubit states, and transitions between them are driven by microwaves at frequencies from 165 to 220 GHz. Electrons on helium provide a beautiful model system, well understood experimentally and theoretically. It can be clearly argued, with some confidence, that they are excellent candidates for condensed matter qubits. They share the scalability of solid state qubits, held in nanofabricated structures, but with long decoherence times . Hence a significant number of gate operations are possible, satisfying a condition for QIP. Our previous breakthroughs include the development of techniques to trap, manipulate and count single electrons in this system and to detect them with a single-electron transistor (SET) electrometer. This detector is of sufficient sensitivity to read-out the quantum state of a single electron. The absorption of microwaves, from transitions between the quantum states, has been observed for a pool of many electrons. International interest in this system is increasing and Royal Holloway has established a clear lead. The challenge to develop a prototype quantum information processor will combine state-of-the-art techniques from low temperature physics and nanophysics.An outline of the research is as follows: the optimisation of the trap laterally confining a single electron on the helium surface; the detection of its quantum state and measurement of its lifetime. A clear strategy has then been formulated to evolve from a single qubit, through two entangled qubits, reaching a linear array of N qubits, with readout based on used of microwaves and radio-frequency SET detection. This experimental strategy will be underpinned by well established links with internationally leading theorists.This research would be undertaker. in the Department of Physics, Royal Holloway, University of London, where extensive facilities and infrastructure for low temperature physics and nanophysics exist. This multifaceted and challenging project involves collaboration of the Low Temperature and Nanophysics Groups at Royal Holloway, and the University of Bristol, with Dr Yuri Mukharsky at CEA, Saclay, and other groups This research will
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