Quantum uncertainty in real time ultrafast squeezed light for quantum communication

An international team of researchers has achieved a breakthrough that fundamentally challenges century-old assumptions about quantum mechanics, successfully capturing and controlling quantum uncertainty in real time for the first time. The landmark study, published October 3 in Light: Science & Applications, demonstrates that Werner Heisenberg's uncertainty principle is not a static limitation but a dynamic, tunable property that can be manipulated with unprecedented precision.

https://pubmed.ncbi.nlm.nih.gov/41038835/

Led by Dr. Mohammed Th. Hassan from the University of Arizona, alongside collaborators from ICFO in Spain and Ludwig-Maximilians-Universität München in Germany, the research team generated the shortest ultrafast squeezed light pulses ever created, spanning frequencies from 0.33 to 0.73 petahertz through an advanced nonlinear four-wave mixing process. These attosecond-scale pulses—lasting just quintillionths of a second—enabled the first direct observation of quantum uncertainty dynamics evolving in real time.

Revolutionary Control Over Quantum Properties

The breakthrough centers on "squeezed light," a quantum state where uncertainty is redistributed between complementary properties rather than eliminated. "Ordinary light is like a round balloon, with uncertainty spread evenly between its measurements," Hassan explained to the University of Arizona News. "Squeezed light—also known as quantum light—is stretched into an oval, where one property becomes quieter and more precise, while the other grows noisier".

The team demonstrated unprecedented control by switching between amplitude squeezing and phase squeezing within their generated pulses, revealing that quantum uncertainty fluctuates and evolves dynamically rather than remaining fixed. This capability allows researchers to tailor quantum noise properties on demand, opening new possibilities for precision measurements and quantum technologies.

Using sophisticated light field synthesizers configured with three distinct spectral channels, the researchers split engineered waveforms into reference and squeezed beams, directing the latter through silicon dioxide where four-wave mixing generated the quantum-enhanced pulses. Their experimental setup achieved squeezing below the standard quantum limit while maintaining attosecond temporal resolution.

Secure Communications

Beyond fundamental physics, the research introduces practical applications in quantum cryptography. The team demonstrated a novel petahertz-scale encryption protocol that embeds information directly into quantum uncertainty fluctuations, creating multiple layers of security against eavesdropping. This approach leverages dynamic uncertainty as an intrinsic protection mechanism, potentially enabling communication networks with unprecedented bit rates and security assurances.

"If someone intercepts data sent with quantum light, the network will immediately detect the intrusion—but the intruder could still acquire some information with a decoding key," Hassan noted. "Using our method, an eavesdropper not only disturbs the quantum state but also must know both the key and the exact pulse amplitude".

The breakthrough establishes the foundation for ultrafast quantum optics and could accelerate development of quantum sensors, next-generation quantum computers operating at attosecond speeds, and secure communication systems that exploit quantum mechanics' fundamental properties for enhanced performance