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Right now, in the world of computing the race is on to create a truly useful and effective quantum computer. Next generation super-computers such as these would pave the way for solving a new realm of problems that are incomprehensible to existing computers.
The benefit of quantum computing is that unlike classical computing it can make good use of the unique ability possessed by subatomic particles to exist in more than one state at any given time. What this means is that whereas the current generation of computers use bits – which is a single piece of information that can exist in one of two states, one or zero – quantum computers make use of quantum bits known as ‘qubits’, instead. Therefore, they have the ability exceed traditional information storage capabilities of one or zero due to the fact they can exist in any superposition of these values.
However, the coherence of a qubit, i.e. its preservation of the superposition, is in a fragile quantum state which be easily destroyed by environmental ‘noise’. Furthermore, this noise that can be generated by electronic systems, heat dissipation, or any impurities present in the qubit itself can lead to critical errors that could prove demanding to rectify.
MIT and Dartmouth College researchers have successfully designed and coordinated the first set of laboratory tests that utilizes a breakthrough method that allows for effective monitoring and detection of the characteristics that troublesome environmental noise generates. This significant leap may offer new insights into microscopic noise mechanisms to further assist the engineering of state-of-the-art processes to protect the fragile qubits.
This is the first concrete step toward trying to characterize more complicated types of noise processes than commonly assumed in the quantum domain. As qubit coherence properties are being constantly improved, it is important to detect non-Gaussian noise in order to build the most precise quantum systems possible.
Lorenza Viola, Professor of Physics, Dartmouth
The technique developed by the researchers separates non-Gaussian noise from the background Gaussian noise, then they were able to reconstruct comprehensive sets of information about these signals by using signal-processing techniques. Thus, offering researchers the ability to generate more realistic noise models, which could go some way toward further protecting qubits by enabling vigorous processes that shields them from certain noise types. This is necessitated by the fact that the development of qubits with fewer defects than previous iterations may lead to an increased presence of non-Gaussian noise.
This is akin to being at a loud party where although it may be difficult to maintain a steady conversation it is still possible, however, when individual voices start to stand-out it can contribute to a breakdown in one’s own thought-process making it much more difficult to sustain continual discussion. “It can be very distracting”, stated William Oliver, an associate professor of electrical engineering and computer science, professor of the practice of physics, MIT Lincoln Laboratory Fellow, and associate director of the Research Laboratory for Electronics (RLE).
For qubits with many defects, there is noise that decoheres, but we generally know how to handle that type of aggregate, usually Gaussian noise. However, as qubits improve and there are fewer defects, the individuals start to stand out, and the noise may no longer be simply of a Gaussian nature. We can find ways to handle that, too, but we first need to know the specific type of non-Gaussian noise and its statistics.
Throughout their research, the team determined that qubits with superconducting capabilities can act as sensors for the noise they generate themselves. In the experiments, they introduced non-Gaussian ‘dephasing’ noise as engineered flux noise that interrupts the coherence of the qubit, this can then be utilized as a measuring tool. “Usually, we want to avoid decoherence, but in this case, how the qubit decoheres tells us something about the noise in its environment,” Oliver says. A detailed description of the process was published in a paper in the journal Nature Communications.
However, while the study won’t make large-scale quantum computers manifest in the immediate future it is still considered highly valuable work as the team bridged the gap between theory and practice. “This research started on the whiteboard. We didn’t know if someone was going to be able to put it into practice, but despite significant conceptual and experimental challenges, the MIT team did it,” said Felix Beaudoin, a former Dartmouth postdoctoral student and vital part of Professor Viola’s team.
The progressive impact this study could have on the future of quantum computing is far-reaching, as well as preserving the integrity of qubits it would enable the computers to be more precise, robust, and dependable. Once the gate is open it is expected quantum computing will allow machine learning to accelerate exponentially which means taking giant steps towards advanced AI systems and even reducing the time to solve a problem from hundreds of years to just a few seconds. In short, we could see quantum computing solving some of humanities most complex and difficult questions.