Chao-Yang Lu

A laser pulse lasting one and a half nanoseconds hits a nonlinear crystal, and a stream of squeezed light is born. That is how an experiment on the Jiuzhang 4.0 quantum processor in China begins.

A laser on a lithium niobate crystal comes to life with a current of 40 milliamps. Its light splits into two streams, each passing through a six-millimeter waveguide, where twin photon pairs are born. One stream rotates the polarization of its twins, after which both flows merge into a common channel.

A single photon passes through two slits and leaves an interference pattern on a screen. Quantum mechanics describes this process with a wave function, but what happens to the particle itself?

Even at absolute rest, atoms emit a faint noise — unavoidable quantum jitter. In the debates between Einstein and Bohr, this noise, like an unceasing whisper, blurs the interference fringes from an atomic slit. Overcoming this limit was considered impossible.