Laser Detector in Two Places: How to Hear a Quantum Field ⚡ экспресс
A practical experiment is proposed to measure the response of a particle detector prepared in a quantum superposition of spatial states, interacting with a relativistic quantum field. A modulated laser beam is split into two arms that pass through a pancake-shaped Bose-Einstein condensate at two distinct spots, then recombine. By heterodyning one output, the differential photocurrent power spectrum reveals a response function matching that of an Unruh–DeWitt detector in a superposition of positions, coupled to a massless scalar field in (2+1) dimensions. Squeezed light allows breaking the standard quantum limit, with a calculated signal-to-noise ratio above 10 across a broad low-frequency range. This experiment paves the way for lab-based tests of relativistic quantum effects tied to the detector’s spatial coherence.
Physicists have proposed an experiment: a laser beam acts as a quantum detector and splits into two beam-ears. Each ear is directed through a tiny cloud of ultracold atoms — in this state, atoms merge into a single wave. The clouds are separated, so the detector is in superposition — it’s as if it’s listening to the field from two positions at once. Then the ears merge, and the light is directed to a photodetector and mixed with a reference beam (like tuning a radio) — analyzing the current beats reveals the response of the Unruh–DeWitt detector, a simple receiver model.
To prevent the field’s sound from drowning in noise, the physicists use squeezed light — here, noise in one quantum property is sacrificed for silence in another. It’s like muting the hum to make out a whisper. That’s exactly how gravitational waves were caught — the tremor of spacetime from black hole collisions. In the new experiment, the signal will be clearly heard: it will exceed the noise by 10 times. This will be the first direct test of how quantum fields sense curved spacetime.
🎯 Mixing the signal with a reference beam, like in a radio receiver, helps pick out weak quantum beats from the noise.
🎬 The idea of an object in two places at once inspires science fiction writers: in Hannu Rajaniemi’s novel 'The Quantum Thief,' the protagonist’s consciousness can be distributed across different points.