Quantum Memories Turn 6-Meter Telescopes into 1.5-km Mirrors

Two 6‑meter telescopes linked by a 1.5‑km fiber and diamond quantum memories can produce interference patterns equivalent to a 1.5‑km mirror.

How the Experiment Works

In February, a Harvard–MIT team published a Nature paper describing a proof‑of‑concept that uses two quantum receivers—each a miniature telescope—separated by only six meters. The receivers sit at the ends of a 1.5‑km spooled optical fiber that carries a weak laser beam. At each end, a quantum memory chip built from a silicon‑vacancy defect in diamond stores the incoming photon’s information as spin states of an electron and a silicon nucleus.

Quantum Memory Details

The silicon‑vacancy center behaves like a pair of qubits: the electron spin and the nuclear spin. When a photon arrives, its polarization is mapped onto these spins, preserving the photon’s phase information for microseconds. By entangling the two memory chips via the laser light, the team can later read out the stored states and reconstruct the interference pattern that would arise from a single 1.5‑km mirror.

From 6 m to 1.5 km Baseline

In classical optical interferometry, photons from separate telescopes are combined in the lab. Losses in the optical path limit the usable baseline to a few meters. Quantum memories sidestep this by holding the photon’s phase until both receivers can be read simultaneously, effectively eliminating loss. The result is an interference fringe pattern that scales with the 1.5‑km separation of the fiber, not the 6‑m physical distance between the telescopes.

Implications for Exoplanet Imaging

A 1.5‑km effective aperture in the visible band would deliver angular resolution on the order of a few microarcseconds—enough to resolve the habitable zones of nearby stars or to map stellar surfaces in unprecedented detail. The technique could also sharpen measurements of stellar diameters and binary orbits, feeding into models of stellar evolution.

Technical Hurdles Ahead

The experiment ran in a laboratory setting; deploying it on the sky will require overcoming fiber‑noise, atmospheric turbulence, and the need for ultra‑stable timing across kilometers. Scaling the baseline further would demand longer fibers or free‑space links, each introducing new decoherence channels.

Road Ahead

John Monnier of the University of Michigan calls the work a “breakthrough” but notes that practical optical interferometers will take decades to build. If the quantum memory technology matures, we could see a new generation of optical arrays that rival the Very Large Array’s 30‑km baseline, but in the visible spectrum.

Looking Forward

If quantum‑enhanced interferometry becomes field‑ready, astronomers could finally combine the light‑gathering power of a kilometer‑scale mirror with the high‑resolution imaging of a radio array, opening a new window on the universe.

Source: Tiny quantum computers could help create giant telescopes
Domain: scientificamerican.com