Recently, a team of researchers at the University of Rochester conducted an experiment where they managed to suspend a nano-sized diamond in free space with a laser. The purpose of the experiment was to measure the amount of light emitted from the diamond, but had the added bonus of demonstrating applications that could be useful in the field of quantum computing.
For those unfamiliar with the concept, quantum computing differs from conventional computing since it does not rely on sending information via a series of particles (electrons) through one-way channels. Instead, quantum computing relies on the process of beaming the states of particles (i.e. a photons quantum properties) from one location to the next.
Since this process occurs faster than the speed of light (as no movement takes place) and qubits (quantum bits) have the ability to be in more than one state simultaneously, computations done using this model would be exponentially faster. But despite many advancements made in recent years, the field remains largely theoretical and elusive.
To conduct their experiment, the researchers focused a laser into a 25 cm (10 inch) chamber and then sprayed an aerosol containing dissolved nanodiamonds inside. These nanodiamonds were attracted to the laser in a technique known as “laser trapping”, until a single particle was isolated and made to levitate. Once the tiny gem was levitating in free space, the researchers used another laser to make defects within the diamond emit light at given frequencies.
This process is known as photoluminescence – a form light emission that is caused by defects in the tiny diamond that allows for the absorptions of photons. When the system is excited, it changes the spin; and when the it relaxes after the change, other photons are emitted. This occurs because nitrogen atoms replace some of the carbon atoms in the diamond. Once the nitrogen is nested in the diamond’s atomic structure, it is possible to excite electrons with a laser.
According to the researchers, this photoluminescence process has the potential to excite the system and cause what is known as Bohr spin quantum jumps, which are changes in spin configuration of the internal defect. This occurs because nitrogen atoms replace some of the carbon atoms in the diamond. Once the nitrogen is nested in the diamond’s atomic structure, it is possible to excite electrons with a laser.
In addition, the potential also exists to turn the nanodiamond into an optomechanical resonator. According to Nick Vamivakas, an assistant professor of optics at the University of Rochester, these are structures in which the vibrations of the system can be controlled by light. Optomechanical resonators have the potential to be used as incredibly precise sensors, which could lead to uses in microchips.
In addition, these resonator systems have the potential to create Schrödinger Cat states, which are typically not found in microscopic objects. As anyone who’ familiar with Futurama or Big Bang Theory may recall, this refers to the thought experiment where a cat is inside a box with poison, and until someone opens the box and determines its whereabouts, the cat could be considered simultaneously both alive and dead.
Being able to stimulate matter so that it can exist in more than one state at any given time is not only revolutionary, it is a clear step towards the creation of machines that exploit this principle to perform computations. According to Nick Vamivakas, an assistant professor of optics at the University of Rochester, explained:
Cat or cat-like states contradict our everyday experiences since we do not see common things in quantum states. The question is: where is this boundary between microscopic and macroscopic? By generating quantum states of larger and larger objects, we can hone in on a boundary … if there is one.
Naturally, the Rochester team is still a long way from achieving their big breakthrough, and Vamivakas himself admits that he does not know how far away a quantum computing truly is. In terms of this latest experiment, the team still needs to cool the crystal better, which they are hoping can be achieved with a few technical improvements. And then they hope to find a better way of running the experiment than spraying nanodiamond dust into a tube.
In the meantime, check out this video of the experiment. It promises to be “illuminating” (sorry!):