Quantum states of photons and relativistic physics on a chip

The fundamental physical models for the macrocosm and the microcosm – general relativity and quantum mechanics – still have not been reconciled. We approach this fascinating borderland through experiments with microwaves and superconducting electronic circuits.

Our team recently developed techniques for creating particles of light – photons – from vacuum. This is a “parametric” effect similar to a child on a swing, who uses his or her legs to gain height. Another example is the parametric amplifier, widely used in electronics and optics. In contrast to the above examples of classical effects, we are going to study quantum parametric effects. We do this in superconducting resonators with controllable boundaries – mirrors for the microwaves. This allows us to mimic mirrors that move very fast, nearly at the speed of light.

We will study three physical phenomena:

·    In special relativity’s twin paradox, one twin travels in a spaceship, while the other twin stays at home; upon return, the traveler is younger than her peer. The paradox is resolved in general relativity by accounting for acceleration. We can now test this on a microchip. By first catching photons between two movable mirrors – in a “spaceship” resonator for microwave photons – we can then controllably move them at almost light speed. We will measure a slow-down of the flow of time for these photons, compared to a clock at rest.

·    The microwave field in the resonator becomes unstable and starts to grow when we shake the resonator vigorously. We then expect a novel state of quantum radiation – a photon condensate – with features related to superconductors and ultra-cold atoms.

·    Building on our unique microwave frequency comb technology we can shake the resonator with multiple tones, and move the mirrors in more complicated ways. We can then generate cluster states – quantum entangled photons of various colors – a resource with exciting properties for quantum-information processing applications.

Partner organizations

• Royal Institute of Technology (KTH) (Academic, Sweden)