Producing Single Photons


photo credits: University of Bath

Researchers at the University of Bath have recently developed a technique to more reliably produce single photons, potentially advancing the field of quantum information processing. The study of the world at the atomic scale is what gave birth to the field of quantum physics. Down at the scale of the “very small” the rules of classical physics break down into counter intuitive concepts such as the superposition of quantum states and quantum entanglement. Although summarizing the foundations of quantum physics rapidly becomes an arduous task, it is possible to conceptualize some of the ideas behind the research undertaken in the department of Photonics and Photonics Materials at our university.

Photons are particles which we know most familiarly as visible light and are ideal entities to use in quantum information technology. However, to maximize their use, we need to be able to produce single photons. As a member of the research team described to the Institute of Physics in a 100 second science video, shining a beam of light through a pair of sunglasses allows the emission of single photons. Although single photons can effectively be produced in this simple way, they emerge at seemingly random time intervals, making their use minimal. However, the team at our university has found a way to surpass this difficulty. Using a combination of fiber optics and fast optical switches the research team implemented a technique called multiplexing to create single photons. This method not only allows for the properties of created photons to be controlled, but also makes their production a reliable process.

So what does it mean for the development of quantum technology and information processing? Taking a closer look into quantum computers gives us a little bit more insight as to why this is an exciting advance. Classical computers contain information in the form of bits with two states: on (1) and off (0). These bits are used in combinations to create logic gates allowing us to compute anything that is in theory computable. However, we are rapidly approaching the natural limits classical computing power. These limits can be pushed by creating smaller and smaller logic gates, but eventually an alternative must be found. In the quantum world “qubits” take the place of bits, and instead of being in one of two states, they can be in a superposition of both at once. This allows an exponentially greater computational capacity. In theory various particles can be used as qubits but each has its practical advantages and disadvantages. The research undertaken by the team in isolating single photons could facilitate their use as qubits.

The behavior of light has been studied for millennia and its applications span across all fields of science. From microscopy, to medical physics, through to the study of stars, they are a particle which we know increasingly more about, and their potential in the world of quantum information processing is not to be neglected.


written by Emily Meads and Laurie Morgan


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