Demystifying quantum computing

Written by Dave Wallace
22nd November 2024

I am fascinated by quantum computers (QCs). Slowly but surely, I am learning more about them (with the emphasis on slowly).

A quantum processing unit (QPU) uses unique properties of quantum physics to solve problems

As part of my journey of discovery, I was keen to demystify the basics and understand more about how QCs work, how they are programmed, what they look like, and where you can find them.

I asked my QC mentor, Sergio Gago from Moody’s, for help, and he connected me with Yuval Boger, Chief Commercial Officer at QuEra Computing.

Yuval introduced himself, telling me that based in Boston, QuEra is the leader in commercialising QC using neutral atoms. It is built on pioneering research from nearby MIT and Harvard and has recently received funding from Google Quantum AI.

I asked Yuval to give me the basics of a QC.

He explained that they are a new type of computer that will not replace existing computers but instead augment them with unimaginable processing power capable of solving particular problems. We will not have a Zoom call that uses a QC anytime soon.

In essence, a quantum processing unit (QPU) uses unique properties of quantum physics to solve problems.

A quantum computer’s basic unit of information is a qubit, or quantum bit, analogous to a bit in a classical computer. Unlike a classical bit, which is always in a state of 0 or 1, a qubit can simultaneously exist in a superposition of both states. This means that the qubit has a certain probability of being measured as 0 and a certain probability of being measured as 1, depending on its quantum state. The actual measurement collapses the superposition into one of these states (0 or 1), but until that point, it can represent both states probabilistically.

A simple analogy is tossing a coin. In classical computing, it is either heads or tails. But a qubit is like a coin spinning in the air, where it’s not just heads or tails — it’s in a mix of both states until you catch it. When you “measure” the qubit (just like catching the coin), it settles into either 0 or 1, but until that point, it holds a combination of both possibilities.

This enables qubits to store and process much more information than classical bits, giving them incredible processing power.

The more qubits a quantum computer has, the greater its processing capabilities. As you add more qubits, the number of possible combinations of 0s and 1s increases exponentially. For instance, with two qubits, there are four possible states (00, 01, 10, and 11). With three qubits, that number rises to eight states and so on, enabling a quantum computer to explore multiple potential solutions simultaneously.

This is especially advantageous for solving complex problems, where a classical computer would need to examine each possibility individually. For example, a quantum computer with 50 qubits could explore more than a quadrillion (10^15) states simultaneously, a task that is practically impossible for a classical computer. QuEra’s QC Aquila operates with 256 qubits.

I asked Yuval how a qubit in a QuEra quantum computer works.

QuEra’s quantum computers use arrays of individual atoms (typically rubidium) held in place by tightly focused laser beams (a technique known as optical tweezers) to perform quantum computations—a process that seems like science fiction.

Each atom functions as a qubit, the basic unit of quantum information. The atoms have electrons occupying discrete energy levels around their nucleus. By shining a laser with carefully tuned energy, QuEra can manipulate an electron between two distinct energy states – a ground state (low energy) and an excited state (high energy). These states are analogous to the classical 0 and 1, respectively.

The principle of superposition allows a qubit (the atom) to exist in a combination of these two energy states simultaneously, represented by a probability distribution that determines the likelihood of finding the atom in either the ground or excited state upon measurement. This capability is a cornerstone of the quantum computer’s ability to perform calculations beyond the capacity of classical computers.

QuEra’s optical tweezers—highly focused laser beams—trap and hold individual atoms in precise positions, preventing them from moving around. The company can dynamically arrange the atoms by manipulating these laser tweezers. When two atoms are brought close together, they can interact through their quantum states. If both atoms are excited to certain energy levels, their states can become entangled.

Entanglement is a uniquely quantum phenomenon where the state of one qubit becomes intrinsically linked to the state of another, such that a change in one instantly influences the other, regardless of distance. This entanglement is a key feature enabling quantum computers to leverage multiple qubits simultaneously for complex calculations.

Finally, a camera system observes and records the final state of each atom after the computation. The outcome of the quantum computation is determined by whether each atom ends up in its ground state (0) or excited state (1).

And it all happens very fast. According to Yuval, the time-consuming part is getting the program ready.

Other companies use alternative methods such as superconducting qubits. This approach relies on superconductors cooled to near absolute zero. The cooling reduces electrical resistance, allowing quantum effects to take hold. These are the classic-looking QCs you see in pictures, which look like old-fashioned fridges.

Another approach is photon-based quantum computers. This method uses photons (particles of light) for quantum calculations. Photonics has potential advantages in terms of speed and low energy requirements.

Unlike Betamax vs VHS, each modality could be suited to different types of problems, so the future may see a combination of these approaches across various industries and applications.

I wanted to understand how a company might engage with a firm like QuEra to get started. Yuval explained that it offers the following options:

Project-based partnerships: It collaborates with clients on co-development projects to solve specific challenges, such as optimising financial portfolios or predicting hurricane severity. Its team leverages expertise in quantum hardware and algorithms to address unique problems.

Cloud access via Amazon Braket: QuEra’s 256-qubit quantum computer is available through Amazon’s Braket service, enabling remote experimentation and solution development. This has proved ideal for companies like JP Morgan and BMW that want to explore quantum computing without owning hardware—only a credit card is needed to get started.

On-premises quantum computers: It also provides quantum computers for organisations with high-security needs, such as government agencies. These on-premises installations offer greater control and seamless integration with classical computers, minimising latency for hybrid processing tasks.

One thing I’ve particularly been wondering about with QCs is energy consumption. Many of the supercomputers that are being built to service our AI requirements, for example, use vast amounts of energy and water. So I wondered whether it would be a similar situation for QCs. I asked Yuval about the energy consumption of the QuEra computers. I was gobsmacked when he told me it was 7 KWh – like using a couple of hair dryers.

A final thought. I recently listened to Professor Brian Cox talk to Joe Rogan on his podcast. Professor Cox spoke about some of the latest theories around black holes, the origins of space and time, and how this is leading to a description of the universe where it looks like a quantum computer.

Professor Cox said: “We think now, from the study of black holes, that space and time emerge from something else… one way to describe it is just a quantum theory. In quantum computing terms, it would be just qubits. So, a network of qubits entangled together, just like a quantum computer… So it’s interesting, but that almost makes the universe look in some ways like a giant quantum computer.”

About the author

Dave Wallace is a user experience and marketing professional who has spent the last 30 years helping financial services companies design, launch and evolve digital customer experiences.