scientists from MIT have created the world’s first controllable photonic probability bit

Quantum randomness is a unique property of quantum physics, which manifests itself in the so-called “vacuum fluctuations”. Vacuum is a space without matter and light, but at the quantum level, even this “empty” space is subject to change or fluctuations. Imagine a calm sea that is suddenly engulfed by waves – it’s like what happens in a vacuum. Previously, these fluctuations allowed scientists to generate random numbers. They are also responsible for many of the amazing phenomena that quantum scientists have discovered over the past hundred years.

Research results published in the journal Science. The authors of the article are MIT postdocs Charles Roque-Karm and Janick Salamin, MIT professors Marin Soljacic and John Joannopoulos and their colleagues.

Traditionally, computers operate in a deterministic fashion, executing step-by-step instructions that follow a set of predetermined rules and algorithms. In this paradigm, if you run the same operation multiple times, you always get the same result. This deterministic approach is at the heart of our digital age, but it has its limitations, especially when it comes to modeling the physical world or optimizing complex systems, tasks that often involve a huge amount of uncertainty and randomness.

This is where the concept of probabilistic computing comes into play. Probabilistic computing systems use the internal randomness of some processes to perform calculations. They don’t just give one “correct” answer, they provide a range of possible outcomes with corresponding probabilities. This makes them suitable for modeling physical phenomena and solving optimization problems where multiple solutions may exist and where exploring different possibilities can lead to a better solution.

However, the practical implementation of probabilistic computation has historically faced a major obstacle: the lack of control over the probability distributions associated with quantum randomness. But research by the MIT team has revealed a possible solution.

In particular, the scientists showed that introducing a weak laser “shift” into an optical parametric oscillator, an optical system that naturally generates random numbers, can serve as a controlled source of “biased” quantum randomness.

“Despite extensive study of these quantum systems, the effect of a very weak bias field remained unexplored,” notes Charles Roque-Karm, one of the researchers. “Our discovery of controlled quantum randomness not only allows us to revisit decades old concepts in quantum optics, but also opens up potential in probabilistic computing and ultra-precise field sensor.”

The team successfully demonstrated the ability to manipulate the probabilities associated with the output states of an optical parametric oscillator, thereby creating the world’s first controllable photon probability bit (p-bit). In addition, the system has shown sensitivity to temporal fluctuations in the bias field pulses, even far below the level of a single photon.

Yanik Salamis, another member of the team, notes: “Our photonic p-bit generation system currently produces 10,000 bits per second, each of which can follow an arbitrary binomial distribution. We expect this technology to evolve in the coming years, leading to higher photonic p-bit rates and a wider range of applications.”

Professor Marin Soljacic of MIT emphasizes the broad implications of the work: “By making vacuum fluctuations a controllable element, we push the boundaries of what is possible in quantum-enhanced probabilistic computing. The prospect of simulating complex dynamics in areas such as combinatorial optimization and lattice quantum chromodynamics simulations is very exciting.”