Scientists develop nondestructive photon measurement for quantum computing

Will Conley - Nov 16, 2013
Scientists develop nondestructive photon measurement for quantum computing

It's a big month for quantum computing. Earlier today we reported that scientists had sustained a quantum computer for 39 minutes at room temperature instead of having to cool it to near-absolute-zero first, meaning we are that much closer to Ludicrous Speed consumer computers. Now it has come to light that photons can be measured, measured, and measured again--without having to absorb and thus destroy them. The upshot? It's a big month for quantum computing. Explanation after the jump.

Normally when photons--packets of light such as might be used as inputs in a quantum computer--are measured (detected), you have to do it with a telescope camera or a particle collider. These technologies destroy the photon so you can only detect it once. But as shown in an article published Nov. 5 in Science, we can now detect a photon by reflecting it off a superposed atomic nucleus.

A superposed atomic nucleus is one that has been induced (through magnets or some other force) to exist in two energy states at the same time. It is either spinning both "up" and "down", or--in the case of the demonstration discussed in this article--in two different energy configurations at the same time. Briefly and crudely speaking, that's like saying a particular piece of fruit is both an apple and an orange at the same time.

When the photon hits the superposed nucleus, the photon toggles the nucleus' superposed state, which can be detected, thus detecting the presence of the photon. The photon gets reflected and changes behavior but does not decay. It can then be measured again and again for increasing accuracy, arriving at more and more certain measurements for the photon.

What does all this imply? Many things, in many sciences. In the case of quantum computing, it means we can establish quantum "logic gates" analogous to the bit-based, "1's and 0's" logic gates used in silicon-based processors. Plug in a piece of data, get an answer based on a dynamically changing set of logic rules.

Except way, way, way faster. How much faster? Tens of thousands of times faster, roughly speaking. Add this story to the one about the room-temperature quantum computer, and you can eventually have a smartphone that makes the fastest modern smartphones look like a stone tablet and chisel.

SOURCE: Ars Technica

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