Quantum Journal

Quantum Optical Breakthrough Reduces Photon Measurement Overhead by 20 Percent

Researchers have developed a novel quantum light test that significantly streamlines photon measurement processes. This advancement offers a more efficient pathway for high-precision quantum optics and information processing.

Scientists may have finally proved that “empty” space isn’t really empty

A magnetar’s colossal magnetic field may have revealed a quantum effect predicted by Werner Heisenberg nearly 90 years ago, in which seemingly empty space alters the behavior of light. If confirmed, the discovery could offer the first direct evidence of vacuum birefringence and open a new window into the strange physics of the quantum vacuum.

Separable Counterexamples to Complementary Quantum Correlations, and Why Random Search Missed Them

The complementary quantum correlations (CQC) relation bounds the sum of two classical mutual informations, obtained from local mutually unbiased measurements, by the quantum mutual information of the premeasurement state. We refute it. Separable rank-two counterexamples exist in every local dimension pair \(m\times n\) with \(m,n\ge3\), with closed-form excess at least \(1/(8m^2n^2)\) nats, and in every qubit--qudit pair \(2\times n\) with \(n\g...

Multicolor nonlinear chiral quantum optics: beyond phase

Chiral quantum nonlinearities that arise when light interacts with quantum emitters are known to modulate only the phase but not the amplitude of scattered photons, enabling the creation of non-reciprocal photonic elements, quantum logic gates, and quantum network protocols. In this work, we show that the addition of a second photon beam drastically changes this picture, enabling both phase and amplitude modulation. Surprisingly, coherent photon...