Durham, NC and Madison, WI--A laser guided by a microelectromechanical beam-steering system that aims and focuses laser light pulses onto single atoms for use in quantum computers has been demonstrated by collaborating researchers from Duke University and the University of Wisconsin-Madison.1
In theory, quantum computers will be able to solve very complex problems if their basic elements, called qubits, remain in a quantum-entangled state for a long enough time for the calculations to be carried out before information is lost to natural fluctuations. One of several promising approaches to quantum computing uses arrays of individual atoms suspended by electromagnetic forces. Laser pulses manipulate the internal states of the atoms that represent the qubits to carry out the calculation. However, the beams must also be focused and pointed accurately enough that light meant for one atom doesn't affect its neighbors.
The micromirrors, each with a radius of 100 µm, directed the beam to each target atom in as little as 5 µs, which is about 1,000 times faster than beam-steering mirrors developed for optical-communications switching. The pulses also correctly manipulated the quantum properties of each target atom--in this case a line of five rubidium-87 atoms--without disturbing any neighboring atoms, which were separated by 8.7 µm.
The groups plan to continue their collaboration, with future experiments targeting two-qubit gates, which are expected to be the basic building block of quantum logic, and atoms confined in larger two-dimensional arrays.
1. C. Knoernschild et al., Appl. Phys. Lett., 97, 134101 (2010); doi:10.1063/1.3494526
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