The realm of quantum mechanics is strange and unintuitive. Quantum physical laws govern the behavior of the nanoscopic: molecules, atoms, and subatomic particles. At this scale, fantastic things can happen. For example, pairs of particles can become “entangled,” meaning their energy states are linked to each other, even if they’re separated by vast distances across the universe. Albert Einstein famously called this “spooky action at a distance” during early investigations of the phenomenon, which is now a fundamental concept in quantum mechanics and central to applications of quantum computing. Quantum computers can solve certain types of problems far faster than conventional computers, but it is still a nascent technology. One way quantum computing can be made more effective is by harnessing the power of molecules rather than atoms to create qubits – the quantum equivalent to classical bits – of information. This was purely theoretical, until recently.

A team of scientists at Princeton University has devised a clever procedure for reliably entangling pairs of individual molecules. They used a system of highly precise laser beams, or “optical tweezers,” in order to manipulate individual molecules of calcium monofluoride (CaF) and entangle them. This is an exciting step forward for quantum information science because molecules are more information rich than atoms. The nucleus of an atom can spin, offering unique energy states useful for encoding qubits. Molecules contain multiple atoms, so they have spin states like atoms, but can also rotate and vibrate, offering far more energy states to encode qubits. 

We may be on the brink of a technological revolution in computation as quantum computing matures. The age of quantum computing may spur advancements in cybersecurity, energy, sensing, and more, in ways that are hard to predict at this stage. For now, the field faces engineering challenges in scaling up and keeping qubits in their entangled states in larger computers.

This study was led by Connor M. Holland, a graduate student in physics, Yukai Lu, a graduate student in electrical engineering, and Lawrence W. Cheuk, an assistant professor in physics, all at Princeton University. An independent group of scientists led by John Doyle and Kang-Kuen Ni at Harvard University and Wolfgang Ketterle at the Massachusetts Institute of Technology published similar results in Science following this study, further validating the exciting new findings. 

Managing Correspondent: Collin Cherubim

Press Article: Physicists ‘entangle’ individual molecules for the first time, bringing about a new platform for quantum science (Princeton University)

Original Journal Article: On-demand entanglement of molecules in a reconfigurable optical tweezer array (Science)

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