Quantum computers will take us beyond the binary age, into a perplexing new era. And they are already here

The future of Computing

JAY ELWES

Each day, humans create 2.5 quintillion bytes of data. A byte is the amount of data needed by a computer to encode a single letter. A quintillion is one followed by 18 zeros. We float on an ocean of data.

You’d arrive at an even bigger number if you put it in terms of “bits”, the ultimate basic building block out of which every wonder of the digital age is built. A bit is simply a one or a zero or, equivalently, a single switch that must be either on or off. Put eight in a row, and you’ve got enough combinations to label and store every character on your keyboard—there are thus eight bits to the byte.

These days your newspapers, your tax records, your shopping list and perhaps your love life are nothing more than a long series of “ons” and “offs” generated by the digital processors that lurk in your phone, your car and your television. The correct sequence of ones and zeros is all that computers need in order to control the traffic lights at the end of your street, run a nuclear power station, or find you a date for next Friday night. From one perspective, they are simply doing—on a vast scale—the tallying and reckoning we have always done on our fingers: on our digits.

The “digital age” is a colossal achievement of human ingenuity. But this world of ones and zeros is not an end state. Humankind has passed through other ages before: bronze, iron, the era of steam and then of the telegraph, each of which constituted a revolution, before being brought to a close by some further advance of human ingenuity. And that raises a question—if our present digital age will pass just like all the rest, what might come after it?

We are starting to see the answer and it looks as though the successor to the age of the digital computer will be a startlingly new kind of device—the quantum computer. This technology has its roots in an intellectual revolution that started in physics around a century ago. The world of quantum physics reaches out into deeply strange territory. There is the “Schrödinger’s Cat” thought experiment, in which the animal inside a sealed box is both alive and dead at the same time. Other phenomena include quantum teleportation, time-traveling particles and multiverse theory.