(PhysOrg.com) -- Random numbers -- numbers without any pattern -- are vital to many applications, such as computer simulations, statistics, and cryptography. There are many ways to generate them using unpredictable physical processes, including electric-signal noise and radioactive decay, but these methods cannot produce the quantities of numbers needed to keep up with the high data-processing rates of today's computers.

A group of scientists seems to have discovered a way around this problem. They have found that the physical chaos present in semiconductor lasers -- laser light produced using a semiconductor as the medium -- can produce good-quality random number sequences at very high rates.

The scientists, from Takushoku University, Saitama University, and NTT Corporation, all in Japan, achieved random number rates of up to 1.7 gigabits per second (Gbps), which is about 10 times higher than the second-best rate, produced using a physical phenomenon. They report this result in the December issue of *Nature Photonics*.

"We have shown that the performance of random number generators can be greatly improved by using chaotic laser devices," said the paper's corresponding author Atsushi Uchida, a researcher at Saitama University, to *PhysOrg.com*. "The rate we obtained is faster than that of any previously reported devices for generating random numbers using physical sources."

Fields and applications that could benefit from their work are numerous, including computational models to solve problems in nuclear medicine, computer graphic design, and finance. Random numbers are also important to internet security.

Generating random numbers using physical sources -- which can be as simple as coin-flipping and tossing dice -- are preferred over other methods, such as computer generation, because they yield nearly ideal random numbers: those that are unpredictable, unreproducible, and statistically unbiased.

Lasers, Uchida and his colleagues have shown, can be excellent physical sources if they are chaotic. This is achieved, in this case, by reflecting part of the laser light back into the laser using an external reflector. This induces chaos, causing the light intensity to oscillate wildly. As a result, the light's electromagnetic signals are highly complex and cover a wide frequency range.

The researchers used a pair of semiconductor lasers in their experimental setup. Each laser is connected to a photodetector, a device that senses and measures light, and each photodetector is connected to an analog-to-digital converter (ADC), which samples the physical light signals and outputs digital numbers. In this case, the specific ADCs convert the signals into random binary numbers suitable for computing and other high-speed data manipulation.

The group achieved a bit rate of 1.7 Gbps, although future work may center on devising laser schemes that can achieving rates as high as 10 Gbps.

__Citation:__ Atsushi Uchida, Kazuya Amano, Masaki Inoue, Kunihito Hirano, Sunao Naito, Hiroyuki Someya, Isao Oowada, Takayuki Kurashige, Masaru Shiki, Shigeru Yoshimori, Kazuyuki Yoshimura and Peter Davis *Nature Photonics* vol, 2, no. 12, pp. 728-732 (2008); DOI:10.1038/nphoton.2008.227

*Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.*

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Realizing quantum bits

## ShadowRam

## CSharpner

## Bob_Kob

## Mauricio

## Quantum_Conundrum

We can see this intuitively by simply picking two infinite sequences and adding them together.

No matter what you do, there is no term which is "random".

A person who does not know what the parent sequences are may believe the daughter sequence is "random" if it so happens he cannot figure it out, but he is only drawing this conclusion from a position of ignorance.

True randomness could only exist under one of the following conditions:

1) Total Chaos

or

2) An all powerful being outside the universe who is in no way subject to any of the laws of the universe intervenes for no reason that has anything to do with the existing laws of the universe. Even this might not even be considered random.

or

3) Human beings are somehow indowed with true free will by such an all powerful being, thus giving rise to "events" that are not caused by the starting conditions.

===

Otherwise, every event that has ever happened in the history of the universe is a direct, inescapable result of the starting conditions.

## Mercury_01

## Yes

Problem is you may need a random generator to find these decimals with for example a montecarlo process.

## Ensa

Chaos and order can both exist in the same universe, one which has predictable processes and unpredictable ones.

unpredictable in this context does not mean that we cannot predict them, it means they cannot be predicted, they are not ordered, these processes exist and are manifest.

There is no need to grasp after them being somehow 'ordered in a hidden way', any more than there is a need to grasp after ordered processes being chaotic fundamentally. While it may be the case that something may have both ordered and chaotic properties that does not make them the same thing, nor does it mean that the order is chaotic or that the randomness is ordered.

## fleem

1. It is a popular misconception that the vast majority of modern scientists embrace the Copenhagen interpretation, which, as it is casually described, "refutes the idea of hidden variables". The Copenhagen interpretation is actually NO interpretation. Its an assumption that the question, "Why are we not able to predict the outcome of a single QM experiment (except statistically)" is simply not to be asked. In essence, its the arrogant statement, "We can't predict the outcomes because they are unpredictable". Talk about arrogance! The idea of hidden variables is alive and well among scientists. Its just that they all realize we do not yet have the understanding to even try to attempt to answer the question, so we can only "shut up and calculate" for the moment.

2. There is no lack of fast random number generators, as this article implies. You can make a fast generator simply by using more parallel slow number generators. A noisy reverse-biased bipolar transistor can generate, in practice, several hundred million numbers per second. Use several of those transistors in parallel and you can supply numbers faster than any modern supercomputer.

-fleem

## CSharpner

## Ellen

## Rossen

## Ensa

The fact that on occasion some scientists have asserted the randomness of something that has later been found to be ordered simply shows the danger in coming to illogical conclusions, it does not support the idea that an apparantly random process may be actually ordered.

Wemight as well say:

"I know it displays the properties and behaviour of evolution, but really it is design"

Or:

"O know it looks like an alloy of silver and gold but really it is strawberry jelly"

Damn, I swore I would not post in physorg threads ever since that 'plane on a conveyor' thing.

*wanders off muttering and shaking his head*

## Assaad33

Is it just by calculating the frequency of each generated number?

## Ensa

That is an indicator, and a good one commonly used, but also a truly random number generator could come up with a series of 00000's arbitrarily long, they would just be randomly occuring zeros.

Getting back to the original point of the article it is important that the numbers produced are not an artifact of any ordered process, but are genuinely not ordered.

Then they may be used in encryption, for instance, without contributing to any weakness.

## Noumenon

Yes, randomness can be measured via probability distributions, which strangely is an order.

It is also defined physically as entropy in thermodynamics (energy != work),... although if one thinks of a gas in a state of maximum entropy, it would appear perfectly ordered (!) in the sense of not having a arbitrary subjective useful order.

## fleem

In the context of 'random number generator' we simply want a certain distribution (although admittedly ~measuring~ that distribution can be problematic).

But in the context of philosophy, the definition of 'random' is more ambiguous. Compressed data can look very random and have a flat distribution (or even Gaussian, if certain coding is chosen) but unzip that file and you might have a Shakespeare sonnet. So philosophically speaking, the definition of 'random' must include the idea of usefulness (most all would agree a Shakespeare sonnet contains more order than the list of the first ten-thousand word from a dictionary).

-fleem

## Soylent

True randomness is a fundamental part of quantum mechanics. It is possible to construct so called hidden variable theories that do not require the statistical nature of quantum mechanics, but they are non-local and even more hard to swallow than quantum mechanics. (local hidden variable theories have been definitively ruled out by Bell test experiments).

## Soylent

Equidistributed and uncorrelated on all timescales and in all dimensions(e.g. if you take triplets of numbers from the old Linear Congruential Generators for pseudorandom numbers you find that all points lie on repeating equidistant planes).

With pseudorandom numbers, the only thing a computer program can generate with deterministic mathematical operations, you get a predictable sequence of numbers that satisfies many but not necessarily all statistical tests for randomness. If you know the internal state and functioning of the generator you can predict each value it spits out.

The abillity to generate the same sequence again by starting from the same seed value can be highly desirable in something like a game(e.g. if you want to be able to generate the same random maze or same random critter given only a single integer), somewhat useful in a monte-carlo simulation(mostly for debugging purposes) and a fatal flaw in cryptography.

## fleem

-fleem

## Yes

I guess the stick with random numbers has less weight.

:)

I fear randomness is the highest order nature can get. We disorder randomness.

## Yes

## fleem

-fleem

## Yes

So you know everything about the origin of gravity and mass. I am impressed.

## Bob_Kob

## fleem

Depends on which definition of "random" is being used. See my Dec 20 post above on the two common definitions.

-fleem

## Yes

The digits of pi are random.

like in 3.1415926535 etc. The sequence 31415926535 etc each digit is a random number in this precise sequence up to infinity.

## Carls