Physicists just broke a "hard limit" on quantum speed by using a clever trick with a few extra particles of light.
arXiv · March 18, 2026 · 2603.16795
The Takeaway
Quantum measurements were thought to have a strict 50% success 'speed limit' when using standard light-based equipment. This study proves that by simply adding a few extra 'helper' photons, researchers can beat this limit, making future quantum communication significantly faster than previously believed possible.
From the abstract
Any quantum state of the radiation field, sliced in small non-overlapping space-time bins is a collection of single-rail qubits, each spanning the vacuum and single-photon Fock state of a mode. Quantum logic on these qubits would enable arbitrary measurements on information-bearing light, but is hard due to the lack of strong nonlinearities. With unentangled ancilla single-rail qubits, an $8$-port interferometer and photon detection, we show any single-rail qubit measurement in the $XY$ Bloch pl