We established that we can not only access the electron spin states, but also sustain an arbitrary superposition of them for 45 nanoseconds. When you bear in mind that it will take us picoseconds to execute laser-based operations to manipulate the spin, it becomes clear that just a fraction of this period is required.
- Mete Atature
A new study has successfully measured the coherence of electron spin – the period of time in which the particle’s elusive quantum state can be read and manipulated – for an electron trapped in conditions that could form the basis of a future quantum internet.
The study, reported in the journal Physical Review Letters, was carried out by researchers at the Universities of Cambridge and Saarbrücken. It reveals the coherence time of an electron trapped in a silicon-based colour centre within a microscopic fragment of diamond. This is a gap, manufactured inside the diamond’s lattice structure, and designed to snare an electron so that it can be manipulated.
At just 45 nanoseconds, the time period for which the electron’s spin is visible seems a miniscule fraction, but for scientists trying to bring this under control, it is, in relative terms, an age.
The “spin” of a particle is its intrinsic angular momentum and can point either up or down. Physicists at numerous leading research universities, including Cambridge, are currently engaged in research which is trying to utilise spin to develop advanced quantum technologies.
In the future, electron spin could be used to represent data and move large amounts of information much faster than is currently possible. This means that better control of spin might well underpin future computing, enable the creation of an entirely new quantum network (or quantum internet), and provide the foundations for a huge range of other technologies, such as advanced sensing devices.
One problem that hinders scientists who are attempting to gain greater command over electron spin for this purpose, however, is that spins in solids cannot be seen, or manipulated, for very long. After a tiny fraction of a second has passed, the spin’s quantum state decays beyond the point of visibility. Therefore, it needs to be retained for long enough for information about the spin to be registered and manipulated.
In the new study, the researchers successfully demonstrated the extent of the coherence of an electron trapped in a “silicon-vacancy” – an impurity in the lattice of carbon atoms that make up diamond. A silicon-vacancy centre provides highly promising conditions for the manipulation of electron spin.
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Image: Atomic structure of the SiV- color center, consisting of an Si impurity (red) situated on an interstitial position along the bond axis and surrounded by a split-vacancy (transparent) and the next-neighbor carbon atoms (grey).
Credit: Mete Atature
Reproduced courtesy of the University of Cambridge
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