16 September 2013

The first self-assembled nanodiamond qubits are the vanguard of the quantum computing revolution

German researchers have devised a technique of creating self-assembled nanodiamond quantum bits (qubits) that could form the basis of quantum computers and storage devices that, unlike every other quantum tech that we’ve seen on ET, could operate at room temperature.

There are many ways of storing quantum data - atom spin, electron spin, photon spin. There are also many different mediums that can act as qubits, too - single atoms, laser light, whole molecules. One combination excels above all others, though: Storing photons in a diamond nitrogen-vacancy center. This is essentially a diamond molecule (carbon atoms), with a single nitrogen atom replacing one of the carbons. It turns out that this nitrogen atom is remarkably good at storing photons, including the quantum data they carry, for incredibly long periods (milliseconds). More importantly, while virtually every other qubit material must be kept at cryogenic temperatures, diamond-nitrogen qubits can do this at room temperature without suffering from decoherence.

The problem so far, though, has been constructing small-enough diamonds that the nitrogen atoms - the individual qubits - are close enough to each other that they can interact. According to Technology Review, the diamonds have to be within 10 nanometers of each other. Now, Andreas Albrecht and fellow researchers at the University of Ulm in Germany have used DNA to build a scaffold that allows six nanodiamonds to self-assemble in a ring, potentially creating a six-qubit room-temperature quantum computer.
A cluster of larger (30-nanometer) nanodiamonds, bonded to an SP1 protein

Basically, Albrecht and co modified a ring-shaped protein known as SP1 so that it can bind with diamond. They then used a laser to slice tiny, 5nm diamonds off a larger diamond, and then dissolved these tiny diamonds in a solution. The solution was sloshed onto the SP1 rings, whereupon six nanodiamonds bond to each ring in a hexagonal formation. These diamonds don’t have the nitrogen vacancy - that would be the next step of the research - but if they did, they would be close enough to carry out quantum computation.

This breakthrough is exciting for two primary reasons: Self-assembly and scalability. If quantum computers are ever to become commercially viable, self-assembly is necessary - the other option, of painstakingly building each qubit by hand with room-sized scanning tunneling microscopes and cryogenic cooling gear, simply isn’t viable. This approach is also scalable, as in it should be possible to build larger DNA scaffolds that can latch onto more than just six diamonds. Future techniques might allow for dozens or hundreds of nanodiamond qubits - and at that point, we’re talking about computing power that would utterly and irrevocably alter the fabric of society.

Now read: Light stopped completely for a minute inside a crystal: The basis of quantum memory

Research paper: arXiv:1301.1871 - “Self-assembling hybrid diamond-biological quantum devices”


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