1 February 2011
First demonstration of coherent control of a quantum multi-resonator architecture
by Kate Melville
Physicists at the University of California - Santa Barbara have put a new slant on the shell game by demonstrating the ability to hide and shuffle "quantum-mechanical peas" - in this case single microwave photons - under and between three microwave resonators acting as quantized shells.
Their paper, published in Nature Physics, is the first demonstration of coherent control of a multi-resonator architecture. This has been a holy grail among physicists studying photons at the quantum-mechanical level for more than a decade.
The apparatus makes use of two superconducting quantum bits (qubits) to move the photons between the resonators. The research team believe that the qubits - the quantum-mechanical equivalent of the classical bits used in a common PC - will play a key role in the eventual development a quantum computer.
"This is an important milestone toward the realization of a large-scale quantum register," said researcher Matteo Mariantoni. "It opens up an entirely new dimension in the realm of on-chip microwave photonics and quantum-optics in general."
The modern take on the shell game happens on a chip where three resonators of a few millimeters in length are coupled to two qubits. "The architecture studied in this work resembles a quantum railroad," explained Mariantoni. "Two quantum stations - two of the three resonators - are interconnected through the third resonator which acts as a quantum bus. The qubits control the traffic and allow the shuffling of photons among the resonators."
Not content with mimicking the shell game, the researchers played a more complex diversion known as the Towers of Hanoi. In the quantum-mechanical version of the Towers of Hanoi, the three posts are represented by the resonators and the disks by quanta of light with different energy. "This game demonstrates that a truly Bosonic excitation can be shuffled among resonators - an interesting example of the quantum-mechanical nature of light," said Mariantoni.
Source: University of California - Santa Barbara