MIT controls quantum randomness for the first time

Pioneering study demonstrates control of quantum fluctuations, opening the potential for probabilistic computing and extremely precise field sensing.

A team of researchers from the Massachusetts Institute of Technology said (with) achieved a milestone in quantum technologies, demonstrating for the first time the control of quantum randomness.

The team of researchers focused on a unique feature of quantum physics known as “vacuum fluctuations.” You might think of a void as a completely empty space without matter or light. However, in the quantum world, even this “empty” space undergoes fluctuations or changes. Imagine a calm sea that suddenly ripples, this is similar to what happens in a vacuum at the quantum level. Previously, these fluctuations allowed scientists to generate random numbers. It is also responsible for many fascinating phenomena discovered by quantum scientists over the past 100 years.

Experimental setup for generating tunable random numbers from vacuum fluctuations. Credit: Charles Roques Karmes, Yannick Salamin

The results were recently described in the journal Sciences, in a paper led by MIT postdoctoral fellows Charles Roques Karmes and Yannick Slamin; MIT professors Marin Soljacic and John Joanopoulos; and colleagues.

Computing in a new light

Traditionally, computers operate in a deterministic manner, executing step-by-step instructions that follow a set of pre-defined rules and algorithms. In this model, if you run the same process multiple times, you will always get exactly the same result. This deterministic approach has been the driver of our digital age, but it has its limits, especially when it comes to simulating the physical world or optimizing complex systems, tasks that often involve huge amounts of uncertainty and randomness.

Technical illustration of generating tunable random numbers from the quantum vacuum. Credit: Li Chen

This is where the concept of probabilistic computing comes into play. Probabilistic computing systems take advantage of the intrinsic randomness of certain processes to perform calculations. It provides not just one “correct” answer, but a range of possible outcomes each with its own associated probability. This makes them inherently well suited for simulating physical phenomena and tackling optimization problems where multiple solutions can exist and where exploring different possibilities can lead to a better solution.

Dr. Charles Roques Carmis, one of the lead authors of the work, is running the experimental system. Credit: Anthony Toliani

Overcoming quantum challenges

However, the practical implementation of probabilistic computing has historically been hampered by a major obstacle: the lack of control over the probability distributions associated with quantum randomness. However, research conducted by the MIT team has shed light on a potential solution.

Specifically, the researchers showed that injecting a weak laser “bias” into an optical parametric oscillator, an optical system that naturally generates random numbers, can serve as a controllable source of “biased” quantum randomness.

“Although these quantum systems have been extensively studied, the effect of the extremely weak bias field has not yet been explored,” says study researcher Charles Roques-Carmes. “Our discovery of controllable quantum randomness not only allows us to revisit ancient concepts in quantum optics, but also opens up possibilities in probabilistic computing and extremely precise field sensing.”

The team has successfully demonstrated the ability to manipulate probabilities associated with the output states of an optical parametric oscillator, thus creating the first controllable photonic probabilistic bit (p-bit). In addition, the system showed sensitivity to temporal oscillations of bias field pulses, even much lower than singletons Photon level.

Dr Yannick Slamin, one of the lead authors of the work, is running the experimental system. Credit: Alison McPassino

Implications and future prospects

“Our optical bit generation system currently allows the production of 10,000 bits per second, each of which can follow an arbitrary binomial distribution,” says Yannick Salamin, another member of the team. “We expect this technology to develop in the next few years, leading to a higher optical bit rate.” And a wide range of applications.

Professor Marin Sulijačić from MIT emphasizes the broader implications of the work: “By making vacuum fluctuations a controllable element, we are pushing the boundaries of what is possible in quantum-augmented probabilistic computing. The potential for simulating complex dynamics in areas such as conformational optimization and quantum chromodynamics simulations is great.” Very exciting.

Reference: “Quantum vacuum bias for controlling macroscopic probability distributions” by Charles Roques-Carmes, Yannick Slamin, Jamison Sloan, Siu Choi, Gustavo Velez, Ethan Koskas, Nicholas Rivera, and Steven E. Coy, John D. Joanopoulos, and Marin Soljacic, July 13, 2023, Sciences.
doi: 10.1126/science.adh4920