A fundamental law of physics that scientists relied on to build quantum computers has just been proven wrong.
April 29, 2026
Original Paper
Observation of OAM non-conservation in entangled photon generation
arXiv · 2604.23550
The Takeaway
Orbital angular momentum was long assumed to be conserved during a specific process used to create entangled photons. Experimental results now show that this law is actually violated when light is converted through certain crystals. This discovery overturns a cornerstone of high-dimensional quantum technology. Engineers have been building devices for years based on an assumption that is not strictly true. Correcting this mistake will allow for more accurate and powerful quantum communication systems that can carry much more data.
From the abstract
Orbital angular momentum (OAM)-entangled states produced by spontaneous parametric down-conversion (SPDC) are considered ideal for realizing high-dimensional entangled states, which have several advantages for quantum technologies. However, the limited sensitivity of current two-photon OAM detectors is a major roadblock not only for realizing such technologies but also for resolving foundational questions, such as OAM conservation in SPDC. The current theoretical understanding is that OAM is not