Quantum computing: Prepare to have your mind blown

[Quartz Obsession] Quantum computing October 26, 2017 It’s time we had a talk about quantum computers—a technology that’s weirder than any sci-fi novel. Companies like [IBM]( and [Google]( are working feverishly to make them a reality, which could have world-changing implications for fields like cryptography and artificial intelligence. It’s not easy to wrap your mind around spooky quantum mechanics. But we’ll walk you through it, with some help from Justin Trudeau. scare quote “The one part of Microsoft where they put up slides that I truly do not understand.” [—Bill Gates on quantum computing]( 0️⃣1️⃣0️⃣1️⃣1️⃣0️⃣ What's so quantum about quantum computing? --------------------------------------------------------------- Traditional computers, like the one you’re using right now, consist of billions of transistors—microscopic devices that can be turned on or off, which translates into a one or a zero. Every email, GIF, Netflix movie, and spreadsheet is ultimately a really long string of ones and zeros. At any given moment, a classical computer can only be in one state—a particular combination of 1s and 0s across those billions of gates. Quantum computers are totally different. 🍎🍊 Different like how? --------------------------------------------------------------- Different in a way so fundamental it’s mind-boggling. At a subatomic scale, particles have the ability to exist in more than one state at a time. Take an electron—it is spinning in every possible direction at once until the moment you measure it. Yes, this sounds crazy when you’re living in the macro world, but it’s true. Now imagine that you’re using a particle to store your data, harnessing quantum weirdness for your own purposes. It can effectively carry out multiple calculations—based on its all-at-once status—and then only at the end of the computation, when you measure it, does it collapse into a single state. Regular computers use bits, which store either a zero or a one. Quantum computers rely on qubits, held in a superposition of zero and one at the same time. 🤓 Wait, super-entangle-what now? --------------------------------------------------------------- Superposition and entanglement are the two core quantum properties that we’re trying to use for computation. [Quantum superposition]( is the phenomenon where a particle exists in all possible states at once—a bundle of probabilities that could end up being either a one or a zero, but only once you measure it. [Quantum entanglement]( is possibly even weirder—it means that intertwined particles (like, say, two photons) are inextricably related to each other, so that you can’t change one without the other changing as well—even if the particles are on the opposite ends of the universe. 📐 Qubits ain't easy --------------------------------------------------------------- Qubits require elaborate machinery to shield them from the outside world, and keep them at a temperature close to absolute zero (-459.67℉ / -273.15℃). That’s because quantum behavior only happens on a microscopic scale. Anything that exposes a qubit to the macro world—even a stray photon or particle of background radiation—could cause it to decohere, losing its superposition or quantum entanglement. 🙀 Is there a cat involved somehow? --------------------------------------------------------------- Right. [Schrödinger’s cat]( is a quantum mechanics thought experiment about a cat in a box that is both alive and dead—until you open the lid to check. If you’re not familiar, [go read about it here](. Pop Quiz Which of the following are not algorithms designed for quantum computers? Shor's algorithmElmo's AlgorithmGrover's AlgorithmSimon's algorithm Correct. You got it—Elmo loves you! Incorrect. Sorry—that does not compute. If your inbox doesn’t support this quiz, find the solution at bottom of email. 🇨🇦 Help me, Justin Trudeau! --------------------------------------------------------------- In April, a reporter challenged the heartthrob Canadian prime minister to [explain quantum computing]( during a visit to Ontario’s Perimeter Institute for Theoretical Physics. He performed quite well (though [not perfectly](. 💫💥📲 Where's my quantum iPhone?! --------------------------------------------------------------- Don’t hold your breath. Quantum computers aren’t just fast computers, and they wouldn’t be much good for apps and games. Many popular accounts of quantum computers talk about their ability to consider every possible solution at once. That’s … not quite right. Here we’re going to paraphrase computer scientist Scott Aaronson (he [spoke with the Washington Post]( back in 2014): (If you aren’t interested in the way quantum mechanics *actually* works, as opposed to how some metaphors approximate it, you can skip the next paragraph.) In quantum mechanics, Aaronson explains, you have to add up a bunch of numbers called amplitudes. There are different ways that an event can take place—some have positive amplitude and some have negative amplitude. They can cancel each other out. The basic goal is to choreograph things so that the wrong answers cancel each other out, while the right answer is reinforced. Quantum computers could theoretically solve some very knotty problems—like how to [predict the weather]( [break encryption schemes]( or [make artificial intelligences much more intelligent](. 🖍🖍🖍 I think I'd understand this better in cartoon form… --------------------------------------------------------------- [This cartoon explanation]( (thanks again, Scott Aaronson!) is a nice parody of an awkward sex ed talk between parents and kids. Even if you don’t get every nuance, it’s a great way of grokking the basic concepts. (Pro tip: You might want to skip over the panel about “two-dimensional Hilbert space.”) [Screen Shot 2017-10-25 at 2.10.25 PM] I'd like to go even further down this 🐰 hole Physicist Richard Feynman was one of the first people to grasp the potential for marrying quantum mechanics and computing. [Here’s his landmark lecture from 1981](. ⏲⏲⏲ So when can I expect to see some quantum action? --------------------------------------------------------------- By the end of 2017—or possibly early next year—Google says it will demonstrate “[quantum computational superiority]( with a custom chip that contains a 7×7 array of qubits. The test will be based on “quantum sampling” of [50 simulated coin flips]( all at once—a task that would take a normal computer billions of years to complete. Experts talk about the number of years before we see a working quantum computer—or alternatively as the year when it actually arrives—as “Y2Q.” (Cute!) Brian LaMacchia, the head of security and cryptography at Microsoft Research, thinks it will be [about 2030](. 🇨🇦💸 But I want a quantum computer now! --------------------------------------------------------------- Well, a Canadian company called D-Wave Systems has been selling quantum computers to clients including Lockheed Martin, NASA, the NSA, and Google for years. But experts have been arguing about them for just as long. The technique D-Wave uses, called “quantum annealing,” is only useful for solving specific kinds of mathematical puzzles called optimization problems. And it’s not [entirely clear that D-Wave outclasses normal computers]( at this task. 😶 Should I be worried about this? --------------------------------------------------------------- Quantum computing could change the world dramatically, starting with the encryption that (mostly) keeps our online information secure. That’s because modern codes rely on complex mathematical puzzles—exactly the kind of task at which quantum computers excel.That has governments and big companies scrambling to future-proof. There are two main approaches: Come up with an algorithm that isn’t vulnerable to quantum computers, or create a new communications protocol that uses quantum weirdness—most likely the “spooky action at a distance” of entangled photons—to communicate over vast distances, in a way that’s theoretically immune to eavesdropping. TALK TO US How do you feel about quantum computing now? [Click here to vote]( A superposition of ecstasy and dreadKeepin' it classicalBuilding one in my garage rn! THE FINE PRINT In yesterday’s poll about [gravedigging]( 37% of you said “suddenly dirt doesn’t feel so dirty.” Today’s email was written by [Adam Pasick](. Images: Giphy, SMBC (comic image). Connie Zhou/IBM (quiz image) The correct answer to the quiz is Elmo's Algorithm. Enjoying the Quartz Obsession? 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