### How Quantum Mechanics Can Help Protect Your Secrets

Most of us aren’t very comfortable thinking about randomness. People like five-year plans and the comfort of “everything happens for a reason.” Even the messy among us claim there’s order in their chaos. Despite this, many processes that are fundamental to our way of life rely on random numbers.
Random numbers are key to stock market predictions, the security behind online shopping, and the integrity of clinical research trials. Last week in The Optical Society’s journal Optica, a team of scientists introduced a new device for generating random numbers that is based on the quantum mechanical properties of light. It is a record-breaking combination of security, size, and speed.

This isn’t the first quantum-based random number generator, but it is the first one small enough to fit in a mobile device and fast enough for commercial applications. It can encrypt phone and video calls in real-time.

 The tiny-yet-fast quantum random number generator.The small chip in the middle of the picture contains two of therandom number generators, which together measure 6 x 2 mm. For comparison, the coin is 16.25 mm in diameter. Image Credit: Daniel Bartolome & Ona Bombí, ICFO.
If you want to send a secret message, you might do it by code. For this to work you’d need a key that correlates a particular letter or word to something else, like a number. If both you and the intended recipient have a copy of the key, and those are the only two copies, your message is likely to stay safe. Unless someone can break the code. This is where random numbers come in. If you chose completely random numbers instead of A=1 and B=2, the code becomes harder to break. Although encryption processes today are more sophisticated, the same bottom line applies.

Random numbers can be generated in two ways, by computer programs or by physical processes. Computer programs are great at generating numbers quickly, but they can’t generate completely random numbers. They are based on logic—you have to tell them explicitly what to do and where to start. That means they can be recreated and hacked. The more a hacker knows about your system the easier it is to break into. Well-designed random number generators can be very difficult to hack, but if you are dealing with banking transactions or national secrets you definitely want something better.

The highest-quality random number generators are based on physical processes, such as the random “white noise” in an electrical component. By turning this noise into an electrical signal, amplifying it so that it’s easy to detect, and then using a digital converter to turn the electrical signal into a string of 1s and 0s, you can generate numbers that are actually random. This means that even if a would-be hacker creates an identical system, his or her system would generate different numbers. At least as far as we know.

To create the highest quality random number generator possible, your best bet is to rely on quantum mechanics. When you observe the results of a quantum mechanical system, the outcome is completely unpredictable. It must be, according to the fundamental uncertainty that underlies quantum mechanics. In addition, methods relying on “white noise” require a fair amount of energy. This isn’t the case for quantum random number generators.

Led by Valerio Pruneri from the Barcelona Institute of Science and Technology and the Institute of Photonic Sciences (ICFO), a team of researchers from Spain and Italy created the new device. Its design is based on something called a photonic integrated circuit (PIC), which is like an electronic circuit, except it uses light and optical components (like lasers) instead of electricity and electrical components. PICs are great for this type of application because you can integrate them with traditional electronics and PICs don’t take very much energy to operate.

The team placed two carefully chosen lasers on a PIC, one that give off pulses of light and another that is always on. The quantum mechanical randomness appears in the signal of the pulsing laser. When the two laser beams interfere, the random property in the pulsed laser signal causes a random change in the brightness of the combined signal. Detectors on the PIC measure the changing brightness. This information can be turned in to an electrical signal, which can then be turned into a random number.

Tests showed that the random number generator works—the numbers are random—and that it is fast and stable. Although this tiny chip might not look like much, it holds the potential to help create a stronger encryption system than anything we have on our mobile devices today. Just keep in mind that even though this advanced technology may make you feel a little more at ease hitting the “Add to cart” or “Send” button in the future, it still can’t tell you whether or not you should.

### How 4,000 Physicists Gave a Vegas Casino its Worst Week Ever

What happens when several thousand distinguished physicists, researchers, and students descend on the nation’s gambling capital for a conference? The answer is "a bad week for the casino"—but you'd never guess why.

### Ask a Physicist: Phone Flash Sharpie Shock!

Lexie and Xavier, from Orlando, FL want to know:
"What's going on in this video? Our science teacher claims that the pain comes from a small electrical shock, but we believe that this is due to the absorption of light. Please help us resolve this dispute!"

### The Science of Ice Cream: Part One

Even though it's been a warm couple of months already, it's officially summer. A delicious, science-filled way to beat the heat? Making homemade ice cream.

(We've since updated this article to include the science behind vegan ice cream. To learn more about ice cream science, check out The Science of Ice Cream, Redux)

Over at Physics@Home there's an easy recipe for homemade ice cream. But what kind of milk should you use to make ice cream? And do you really need to chill the ice cream base before making it? Why do ice cream recipes always call for salt on ice?