An Isaac Newton Institute Workshop

Entanglement and Transfer of Quantum Information

Erasable Electrostatic Lithography for Quantum Components

29th September 2004

Authors: Charles G. Smith (SP Cavendish Laboratory University of Cambridge), Rolf Crook (), A C Graham (), I Farrer (), H E Beere (), D A Ritchie ()

Abstract

Erasable Electrostatic Lithography for Quantum Components C G Smith, R Crook, A C Graham, I Farrer, H E Beere, and D A Ritchie Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom

Erasable electrostatic lithography (EEL) is a new lithographic technique where patterns of charge are drawn on a GaAs surface with a low-temperature scanning probe [1]. The surface charge locally depletes electrons from a subsurface 2D electron system to define a quantum component ready for measurement in the same low-temperature high-vacuum environment, enabling short lithography to measurement cycles and high productivity. Charge patterns are erased locally with the scanning probe or globally by illuminating the sample with red light. We demonstrate how ballistic 1-D channels can be created at 100 mK then erased and replaced by a small and the large quantum dot. We provide background and characterization data for the EEL technique and then describes the construction and measurement of a quantum billiard. A quantum billiard is a large open quantum dot which exhibits both chaotic behavior and classical orbits. Scanning probe images, made with the same apparatus in the same environment, reveal features associated with the classical closed-loop electron trajectories inside the quantum billiard. This new low temperature technique is ideally suited to the fabrication of the complex quantum architectures required for quantum computation. On of the big problems found when trying to fabricate QBITs using semiconducting quantum dots is that random impurity potentials make each dot different. In order to solve this problem each dot needs several dedicated gates to tune the system. With 10 000 QBITs it is possible that 30-50,000 gates would be required. With our EEL technique it is possible to use deposited charge to tune each QBIT to be in an ideal configuration. This greatly reduces the complexity of the resulting structure. 1. R. Crook, A. C. Graham, C. G. Smith, I. Farrer, H. E. Beere, D. A. Ritchie. NATURE 424 (6950): 751-754 AUG 14 (2003) Erasable electrostatic lithography for quantum components

2. R Crook, C G Smith, A C Graham, I Farrer, H E Beere, and D A Ritchie, 2003 Phys. Rev. Lett. 91, 246803 (2003) Imaging Fractal Conductance Fluctuations and Scarred Wave Functions in a Quantum Billiard

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