Many great discoveries in modern physics depend on the invention of sensors based on new principles. For example, in 1887, an optical interferometer — a sensor based on wave interference — was used to disprove the existence of luminiferous aether, a universal medium through which light waves were thought to propagate1. In 1968, radio telescopes were used to discover extreme astronomical objects known as pulsars2. And in 2016, a laser interferometer was used to detect gravitational waves3. Writing in Nature, Becker et al.4 demonstrate how space-borne sensors based on an exotic state of matter called a Bose–Einstein condensate might provide the next big discovery.
A fundamental principle of quantum physics is wave–particle duality, which describes elementary particles in terms of quantum-mechanical waves (de Broglie waves). The higher the velocity of a particle, the shorter the wavelength of the de Broglie wave. For a cloud of hot atoms, the de Broglie wavelengths are so short that each atom can be considered as an individual object (Fig. 1a).
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