Study shows quantum fluctuations may be controlled, opening the door to extremely accurate field sensing.

By showing for the first time that quantum randomness may be controlled, a team of researchers from the Massachusetts Institute of Technology has made significant progress in the field of quantum technology.


The study team concentrated on "vacuum fluctuations," a special property of quantum physics. A vacuum is sometimes thought of as a fully dark and empty area. Even this "empty" area, nevertheless, suffers oscillations or changes in the quantum universe. The emergence of waves in a calm sea is analogous to what occurs at the quantum level in a vacuum. In the past, these variations have enabled scientists to produce random numbers. The numerous amazing phenomena that quantum physicists have uncovered over the past century are also due to them.
The research results are presented in an article co-authored by MIT professors Marin Soljai and John Joannopoulos, MIT postdoctoral fellows Charles Roques-Carmes and Yannick Salamin, and colleagues that was published today in the journal Science.

Traditionally, computers operate in a deterministic manner, carrying out sequential instructions in accordance with a preset set of rules and algorithms. According to this paradigm, repeating an operation will always result in the same result. Our digital era has been propelled by this deterministic approach, but it is not without its drawbacks, particularly when it comes to replicating the real world or optimizing complex systems, which can include high levels of uncertainty and unpredictability.

The idea of probabilistic computing is used in this situation. Systems that use probability make use of the inherent unpredictability of some processes to carry out calculations. Instead than only giving one "correct" response, they offer a variety of options, each with a corresponding probability. This naturally makes them well-suited to imitate physical events and take on optimization challenges where there may be several possible answers and where exploring several options may result in a superior one.

However, a fundamental barrier that has historically prevented the practical application of probabilistic computing is the inability to regulate the probability distributions connected to quantum randomness. However, the MIT team's study has shown a potential fix.

In particular, the researchers have demonstrated that a weak laser "bias" may be used to controllably produce "biased" quantum randomness in an optical parametric oscillator, an optical device that naturally creates random numbers.


Charles Roques-Carmes, one of the study's researchers, claims that "despite extensive study of these quantum systems, the influence of a very weak bias field was unexplored." The ability to controllably generate quantum randomness "allows us to revisit decades-old concepts in quantum optics and opens up potential in probabilistic computing and ultra-precise field sensing," the authors write.

The group has created the first-ever controlled photonic probabilistic bit (p-bit) by successfully demonstrating their capacity to change the probabilities linked to the output states of an optical parametric oscillator. The system has further demonstrated sensitivity to the temporal oscillations of bias field pulses, even at levels considerably below the level of a single photon.

Another team member, Yannick Salamin, says, "Our photonic p-bit generating technology now enables the synthesis of 10,000 bits per second, each of which may follow any binomial distribution. In the next years, we anticipate that this technology will advance, bringing forth higher-rate photonic p-bits and a wider range of applications.

We are pushing the limits of what is feasible in quantum-enhanced probabilistic computing by making the vacuum fluctuations a controlled factor, says MIT Professor Marin Soljai, who highlights the work's wider ramifications. It's quite intriguing to think about simulating complicated dynamics in fields like combinatorial optimization and simulations of lattice quantum chromodynamics.