Abstract

The theory of quantum mechanics was developed at the beginning of the twentieth century to better explain the spectra of light emitted by atoms. At the time, many people believed that physics was almost completely understood, with only a few remaining anomalies to be ‘ironed out’. The full theory of quantum mechanics emerged as a completely unexpected description of nature at a fundamental level. It portrays a world that is fundamentally probabilistic, where a single object can be in two places at once—superposition—and where two objects in remote locations can be instantaneously connected—entanglement. These unusual properties have been observed, and quantum mechanics remains the most successful theory ever developed, in terms of the precision of its predictions. Today, we are learning how to harness these surprising quantum effects to realize profoundly new quantum technologies. This lecture will examine how single particles of light—photons—are being used to develop secure communication systems based on the laws of physics, precision measurements using entangled light, and information processors that promise exponentially greater computational power for particular tasks.