Security in the digital world traditionally relies on mathematical equations to protect data. For example, when using a credit card online, information is protected by a complex mathematical problem that a modern computer would take thousands of years to solve. However, if a powerful enough computer is created, this protection will cease to work. To make systems more reliable, there is a growing shift towards quantum security, which uses immutable laws of quantum physics instead of traditional mathematics.
Prabhanjan Anand from UC Santa Barbara (USA) and Amit Sahai from UCLA (USA) described a method that makes this quantum protection faster and more efficient. Their work was published on the arXiv preprint server and has not yet been peer-reviewed.
How the Method Works
The system is based on the no-cloning theorem—a fundamental rule of quantum physics that establishes the physical impossibility of creating an identical copy of an unknown quantum state. This is directly opposite to the usual digital world, where any file can be copied infinitely many times perfectly.
Based on this principle, Anand and Sahai developed a way to encrypt a single bit of a message—a simple 0 or 1—into quantum encrypted text. A secret digital key scrambles the hidden bit along a sequence of quantum states. When these states are measured together, they reveal the secret bit. The authorized recipient uses the same key to read the states and obtain the correct message.
Why Interception Fails
The system is designed to block a specific type of attack where an attacker intercepts the data and splits it between two accomplices. According to the rules of quantum physics, any attempt to split quantum data disturbs the information, making it impossible for both accomplices to read the secret.
Even if the accomplices later obtain the secret key, quantum physics does not allow them to reliably reconstruct the message. The researchers demonstrated that the more quantum states used, the closer the chances of both parties correctly determining the hidden bit approach the probabilities of a random coin toss—50/50. When the result does not exceed randomness, the encryption performs its function.
In the paper, Anand and Sahai claim that their approach overcomes previous limitations: 'We have eliminated all these caveats by showing that there exists an efficient, one-time, and information-theoretically secure non-clonable encryption.' The authors also emphasize that the 'scheme is exponentially secure,' as the protection increases with each additional quantum state used.


