Quantum computers are still in a very early experimental stage. Even the underlying technology best used to implement a quantum computer hasn’t yet been settled upon. The problem is that qubits, the basic objects that a quantum computer works with, are very difficult to control. So it’s not surprising that the larger scale architecture of quantum computers is also not yet determined. Up until now, experimental architectures have not been like the easily reprogrammable Von Neumann architecture of all modern electronic computers. But finally that architecture is being explored for quantum computers.
Today, Matteo Mariantoni at the UC Santa Barbara and pals reveal the first quantum computer with an information processing unit and a separate random access memory.
Their machine is a superconducting device that stores quantum bits or qubits as counter-rotating currents in a circuit (this allows the qubit to be both a 0 and 1 at the same time). These qubits are manipulated using superconducting quantum logic gates, transferred using a quantum bus and stored in separate microwave resonators.
Let’s say upfront that the result is not a particularly powerful computer. Mariantoni and co show off their device by demonstrating a couple of simple but unspectacular algorithms but ones that were carefully chosen as the building blocks of more impressive tasks such as error correction and factoring large numbers.
Not that they’ve actually done any of those things. What’s impressive, however, is that they soon could since this approach is eminently scalable.