Quantum computing – widely called the holy grail of tech research – has taken another step towards reality, thanks to a group of researchers at Yale University. The team recently developed a new way to change the quantum state of photons, the elementary particles researchers hope to use for quantum memory.

The research was published in this month's edition of Nature, and it's available on the web at arXiv.

Today's computers store information as bits, where each bit holds either a "1" or a "0." But a quantum computer is built around quantum bits, or qubits, that can store a 1, a 0 or any combination of both 1 and 0 at the same time. For example, a qubit could be 90 percent "0" and 10 percent "1."

So far, all we've seen are some proofs of concept that can do simple calculations, but a full-blown quantum computer consisting of many qubits would be able to perform complex calculations far outside the limits of even the most powerful of today's supercomputers.

In a quantum computer, the qubits will make up the equivalent of a processor. But you'll also want some sort of quantum RAM. Gerhard Kirchmair – one of Yale researchers – explains that photons are a good choice for this because they can retain a quantum state for a long time over a long distance. But you'll want to change the quantum information stored in the photons from time to time. What the Yale team has developed is essentially a way to temporarily make the photons used for memory "writeable," and then switch them back into a more stable state.

To do this, the researchers take advantage of what's known as a "Kerr medium." A normal material will refract light – or any other electromagnetic field – the same way, regardless of how much light you shine on it. But Kerr media will refract a stimulus in a different way depending on the level of stimulus. The quantum state of photons in a Kerr medium can be easily manipulated with a microwave field.

But always storing these memory photons in a Kerr medium would be too unstable, so the researchers found a way to make a vacuum within an aluminum resonator into a Kerr medium on demand by coupling it with a qubit. When the resonator is decoupled, the photons are stable. When resonator is coupled, the photons are "writeable."

Other researchers had found more complex ways of changing otherwise stable photons, but Kirchmair says their method is more simple and practical.

This is but one of several important steps required to make quantum computing practical. Last year, researchers announced a new way to create photons, and others developed single atom transistors.