Quantum Computing
Not to be confused with "Quantum Leap"
What does one have to do with the other? Nothing at the present time. But science fiction has had an amazing run of predicting future technology, though the actual development hasn’t always taken place precisely in the envisioned manner.
Today, the idea of leaping through time (as related in the TV series Quantum Leap) is strictly in the realm of fiction. But who knows what the future might hold.
So let’s return to the real (if fantastical) world of quantum mechanics and computers. The very real activity called quantum computing is under development by IBM and others. What is it?
But first a bit of history: The term “computer” didn’t initially refer to a a machine; no, it was a woman’s job description. Women were in computing from its earliest days. They were essential when “computers” weren’t yet machines. Before the digital age, women (i.e., computers) performed math by hand. In the 1890s, Harvard Observatory decided to process years of astronomic data it had gathered using its telescope. So it assembled an all-woman team of computers. They were paid less than half of what men would have been paid despite the fact that these women actually had to have pretty advanced math skills and math training, especially if they were doing very complex calculations.
(Nothing ever changes.)
In World War II, over 200 women were hired at the University of Pennsylvania to create artillery-trajectory tables for the Army. And as is well known now, NASA employed women – many of whom were Black – as computers. (Mathematician Katherine Johnson, a Black woman, was one of the “computers” whose calculations helped NASA achieve manned spaceflight.)
IBM Quantum lab in Yorktown Heights, NY
The above photo reminds me of the early days of computers when vacuum tube technology, not solid-state devices, ruled the day. Those early machines had to be installed on special flooring to provided isolation from external vibration. And the rooms that housed those computers required tons of air conditioning to dissipate the heat that was generated by those behemoths.
(The electricity bill must have been astronomical.)
Today, computing devices, which are not always called computers, are ubiquitous. Let’s start with the one most people carry with them on a daily basis: a smartphone. It uses a binary system of coding (0 and 1) to perform all manner of operations. The same principle is used in a tablet or laptop or desktop machine. (You can think of a supercomputer as nothing more than an array of smart phones.)
To give a sense of the speed of these devices, performance is usually measured in something called floating-point operations per second (FLOPS). Supercomputers can perform over a hundred quadrillion FLOPS. A typical desktop computer has performance in the range of hundreds of gigaFLOPS to tens of teraFLOPS. The Apple-12 iPhone can perform 11 trillion FLOPS.
BTW, the 1980s Cray-2 supercomputer could perform 1.9 billion FLOPS. The Apollo 11 guidance computer could only perform a bit more than 11 thousand FLOPS.
So your smartphone has more computing power than what was available to the astronauts in 1969 or the Cray-2.
Back to quantum computers. But don’t expect to see one on your desktop (much less your smartphone) anytime soon, and maybe not in a century or two.
So, whereas a conventional computer uses bits — a stream of electrical or optical pulses representing 1 or 0 — quantum computers use qubits, which are typically subatomic particles such as electrons or photons (e.g., the spin of an electron or the orientation of a photon). The objective is to isolate the qubits in a controlled quantum state. To achieve this, some companies use superconducting circuits cooled to temperatures colder than deep space. Others trap individual atoms in electromagnetic fields on a silicon chip in ultra-high-vacuum chambers.
Qubits have weird quantum properties: These are known as superposition and entanglement. The end result is that a connected group of qubits can provide more processing power than the same number of binary bits.
For example, eight bits in a current computer can represent any number between 0 and 255. However, eight qubits in a quantum computer can simultaneously represent every number between 0 and 255.
This is where quantum computers get their edge over conventional ones. Where there are a large number of possible combinations, quantum computers can consider them simultaneously.
Qubits can represent numerous possible combinations of 1 and 0 at the same time. This ability to simultaneously be in multiple states is called superposition.
Researchers can generate pairs of qubits that are “entangled,” which means the two members of a pair exist in a single quantum state. Changing the state of one of the qubits will instantaneously change the state of the other one in a predictable way. This happens even if they are separated by very long distances.
The spooky behavior of entanglement baffled even Einstein. Suffice it to say that in a conventional computer, doubling the number of bits doubles its processing power. But because of entanglement, adding extra qubits to a quantum machine produces an exponential increase in its number-crunching ability.
(I don’t pretend to understand any of this on a technical level. It’s way above my pay grade.)
Of course there’s a downside to everything. In the case of a quantum computer it’s the instability of the quantum state, which is extremely fragile. As of now, quantum computers are highly sensitive to heat, vibration, electromagnetic fields and collisions with air molecules. These can cause the system to crash. If the computation hasn’t been completed when that happens, you’re back to square one. That’s why quantum computers are contained in supercooled refrigerators and high-vacuum chambers.
By the way, the quantum processor is a wafer that is not much bigger than the one found in a laptop. But the support system can be the size of a small car.
Despite these operational problems, companies are using first-generation quantum computers to try and solve real world problems. Some examples: simulation of the chemical composition of EV batteries to improve their performance; analyzing and comparing compounds that might lead to new drugs; rapidly crunching through large numbers of potential solutions to optimization problems.
The guts of a quantum computer
I have to say that these photos of the guts of a quantum computer do have a Sci-Fi quality about them. It’s something I would expect to see on the set of a fictional story such as Quantum Leap.