In a quantum computer, the equivalent of bits that hold binary information as 1s and 0s in todays computers will be quantum bits or qubits, which can also exist as superpositions of 1s and 0s. This massively increases the amount of information that can be encoded in a quantum computers memory. The catch is that superpositions are extremely delicate and hard to maintain, especially in memories containing large numbers of qubits that interact with one another.
Various candidates for making qubits are being explored, such as magnetically trapped atoms or nanometre-scale blobs of semiconductors. But it has long been recognized that loops of superconducting material can also be placed in quantum superposition states, and thus act as qubits. Here the quantum states may correspond to an electric current circulating round the ring in one direction or the other. (In superconductors this circulation can continue more or less indefinitely without petering out, because there is no electrical resistance.)
At the conference, Simmonds will describe the first demonstration of information being transmitted between two such superconducting qubits. This shows that elements of this kind can act as a quantum-computing memory and a bus for qubits to communicate with one another, an essential requirement of any working computer.
The two superconducting loops are made from thin wires of aluminium laid down on a slice of sapphire and cooled to less than 0.1 degrees of absolute zero to make them superconducting. They sit just a millimetre apart, but are connected by a meandering waveguide 7 mm long a kind of light channel, like an optical
|Contact: Joe Winters|
Institute of Physics