Quantum mechanics provides the only immutable source of raw entropy

The Physics Behind the Power of Great Entropy

Entropy is all around us and yet is an elusive prize. Entropy is the measure of uncertainly or disorder within a set of data. The higher the level of uncertainty or unpredictability the more random the data is and the more valuable it becomes, particularly for cryptographic operations.

There are many ways to capture and generate entropy, all are associated with physical processes. These sources generally fall into three categories –

  • Things we see, hear and do:
    • Sounds captured by a microphone
    • Video captured by a camera
    • Mouse clicks and keyboard strokes
  • Processes within the host computer:
    • Network interrupts
    • Hard drive activity
    • Software timing
  • Independent sources of ‘noise’:
    • Thermal and electrical noise
    • Electromagnetic radiation
    • Magnetic fluctuations
    • Quantum effects

The ‘quality’ of these various sources varies enormously and measuring the level of entropy in the data that they generate is notoriously difficult.

There are various statistical tests for bias and the distribution of ones and zeros in the overall data set but ultimately the critical assessment is whether or not a potential attacker is able to predict or know the random data that was used. This boils down to three questions:

  • Can the attacker simply get a copy of the same entropy?
  • Can the attacker reasonably predict the entropy that was collected?
  • Can the attacker influence the entropy that is collected – essentially substituting his or her own entropy?

It is clear that some of the common sources of entropy fail all three of these tests and should not be used as the sole source of entropy in security systems. Some can pass the first test and others the second but almost all sources fail the last test, they are to some degree subject to external influence – the only exception is quantum.

The sources of randomness used by non-quantum random number generators can all be described by “classical” physics; this means that their output can in principle be completely predicted. Though the output may appear jumbled, any output value is determined by the previous values—they are not independent. Only quantum systems are able to produce output values that are truly unpredictable and independent from one another. This is because the behavior of the universe at the smallest scale – the quantum level – is fundamentally unpredictable.

The Entropy Engine from Whitewood makes measurements on a specially-prepared quantum optical field. The outcomes of these measurements are completely determined by the underlying quantum fluctuations. Signal processing stages within the Entropy Engine create digital bits from these measurements to provide pure random numbers to the user.



This White Paper addresses the fundamental questions about entropy. What role does it play in creating random numbers, how can it be measured and how can the various methods for generating entropy be compared?

The white paper is authored by Richard Hughes and Jane Northolt, the co-founders and co-leaders of the Quantum Communications team at Los Alamos National Laboratory. The paper provides technical details on how quantum mechanics is the truest form of entropy generation and considers the benefits of new techniques such as photon bunching.

Finally, the paper describes the architecture of the high-performance Whitewood quantum-powered random number generator, the Entropy Engine.

Whitewood is a subsidiary of Allied Minds Federal Innovations, the division of Allied Minds dedicated to commercializing U.S.federal intellectual property. Allied Minds is an innovative U.S. science and technology development and commercialization company. Operating since 2006, Allied Minds forms, funds, manages and builds products and businesses based on innovative technologies developed at leading U.S. universities and federal research institutions. Allied Minds serves as a diversified holding company that supports its businesses and product development with capital, central management and shared services. More information about the Boston-based company can be found at