From the moment it was first ignited in an old hermit’s home in the middle of Tatooine, the lightsaber captured the imagination of moviegoers. The steady humming of a blue blade of plasma bouncing off its scarlet counterpart has made generations of fans all over the world want one of their own. Made popular by the Star Wars Episode IV: A New Hope, the lighsaber has generated quite a legacy for itself.
Lightsabers have remained in the realm of fiction ever since they first appeared on screen. No known physics model could explain the ways the bars of light made contact with each other. However, this past September, recent findings by a team of scientists from Harvard and Massachusetts Institute of Technology (MIT) showed light behaving in a fashion reminiscent of the blade of the lightsaber.
Harvard Professor of Physics Mikhail Lukin and MIT Physics Professor Vladan Vuletic managed to bind photons—particles of light—together to form molecules. Using weak laser pulses, the scientists shone photons through a special medium—a cloud of rubidium atoms—in a chamber just a few degrees above absolute zero. Normally, photons are described as massless particles that do not interact with each other; when you shine two rays of light together, the beams simply pass through one another. However, when Lukin and Vuletic sent two photons through the special medium, the particles escaped the other end as a single molecule.
This phenomenon—where the photons clumped together as if they had mass and formed molecules—can be explained through the Rydberg Blockade concept. As the photons travel through the cloud, their energy excites the rubidium atoms in the medium along their path. This excitation causes the photons to interact in such a way that they slow down tremendously. The photons regain their normal behaviour once they leave the special medium, exactly like when light passes through water or a prism.
While Star Wars fans would love their own lightsabers, the motivation behind this particular research was instead its potential applications in quantum computing—a field introduced in the ’80s by mathematician Yuri Manin and theoretical physicist Richard Feynman.
Quantum computers are similar to current computers on the market, except that instead of using bits as a storage basis, they use qubits. A bit represents a 1 or 0 in classical computers, and is simply an electrical switch, which can be either on or off. A qubit, on the other hand, relies on the quantum mechanical notion that something can exist in all its states at once.
As computers progress, the size of their processors continue to get smaller. There is a limit to this, however, and manufacturers are rapidly approaching the smallest sizes possible. Theoretically, quantum computing would help increase computers’ processing power.
Lukin and Vuletic’s findings provide a clue in the direction of the storage of quantum information and on the process of inducing photon interaction—two important concepts for designing a quantum computer.
With the discovery of a new state of matter comes a veritable flurry of new applications. In an interview with the Harvard Gazette, Lukin suggested that by utilizing this phenomenon crystal structures could one day be made entirely out of light. The day we all own our own lightsabers might not be so far off.
Despite the fact that these “blades of light” do not radiate heat, generate energy, nor can they be contained in a single hilt at the moment, these findings just go to show that science will go to the greatest of lengths to realize the impossible.
