What is Quantum Computing? A Beginner's Guide to the Computer of the Future

The idea of quantum computing may feel a lot like stepping into the world of Marvel Studios’ Ant-Man series and exploring the Quantum Realm. In the movies, Scott Lang and his team venture into a bizarre space where the usual rules of physics don’t apply, unlocking incredible, almost magical possibilities.

Like the Quantum Realm, quantum computing challenges our understanding of how the world works. By tapping into the principles of quantum physics—like superposition (the ability for quantum bits or qubits to exist in multiple states at the same time) and entanglement (the process of linking qubits so that the state of one instantly reflects changes in another)—quantum computers can do things that seem almost impossible.

Scientists and researchers are beginning to harness the power of the quantum realm to build powerful computers with the capability to break the world’s encryption algorithms.

Before we can dive into quantum computing, though, we have to understand quantum physics.

What is quantum physics?

Quantum physics, or quantum mechanics, is the branch of physics that deals with how things behave at extremely small scales, like atoms and subatomic particles. Unlike conventional physics, where things are predictable, and calculations are precise, in the quantum world, we can only use probabilities to predict how things will behave.

In the quantum world, particles can act like both individual units and waves simultaneously, with their state changing when measured. Quantum computers use these principles, performing calculations based on the probabilities of quantum states, taking advantage of superposition and entanglement before those measurements take place.

In quantum computing, superposition lets a quantum bit—known as a qubit—exist as both 0 and 1 at once until measured, while entanglement links qubits so that knowing one’s state reveals the other’s, no matter the distance. Qubits let quantum computers solve problems in ways conventional computers can’t.

“There’s a quantum realm in our computer where Newton’s laws of physics don’t apply,” Director of Computational Theory and Design at Quantinuum, David Hayes, told Decrypt in an interview. “The trick is to keep that tiny space isolated from the rest of the lab. You don’t want that little region to interact with the outside world—that’s the only way to preserve its quantum state. It has to be completely isolated,” he explained. “That’s the quantum realm. That’s the Ant-Man realm.”

Launched in November 2021, Colorado-based Quantinuum develops solutions for cybersecurity, drug discovery, material science, finance, and natural language processing.

As Hayes explained, quantum researchers use lasers and electric fields to reach into the quantum realm.

“In a conventional computer, you apply voltages to transistors,” he said. “Here, you're applying laser pulses that hit the atoms and manipulate the information that way.”

The idea of quantum mechanics can be traced back to research in 1900 by Max Planck, who is considered the father of quantum theory. Quantum computers would come later in the 1980s and 1970s when Paul Benioff proved it was possible to build a computer that operated under the laws of quantum physics. In 1994, MIT Professor of Applied Mathematics Peter Shor developed his Factoring Algorithm, later known as Shor’s Algorithm, which showed that a quantum computer could efficiently factor large integers, breaking RSA encryption—a cornerstone of modern cryptography.

Shor’s discovery, which remains the standard for quantum computing, underscored the practical power of quantum computers and spurred a surge of investment and research into quantum computing, accelerating its development over the next 30 years.

What is quantum computing?

Unlike supercomputers like the Lawrence Livermore National Laboratory’s El Capitan, recently declared the world's fastest computer and capable of 2700 quadrillion operations per second, quantum computers perform computations by exploring multiple possible solutions simultaneously. This is possible because qubits can exist in a superposition of states, allowing them to handle multiple computations at once.

Hayes noted, however, that in regard to actual clock speed, the number of cycles a computer's central processing unit (CPU) can perform per second, quantum computers are not “faster” than conventional computers.

“Even though the individual operations might happen slower, you have to do way less of them in order to solve a problem, sometimes exponentially fewer,” he said.

How are quantum computers made?

Traditional computers are made up of millions of tiny switches that manage the flow of electrons. But as we have shrunk those gates down to the sub-atomic level, the ability to control whether electricity flows through a gate or not becomes like trying to herd a swarm of ants. Through quantum tunneling, when we get to the sub-atomic level, electrons can simply hop over the gate at will, rendering a machine's ability to manage that flow useless. As a result, quantum computers are made very differently.

Unlike traditional logic gates that simply process signals as 0s or 1s, quantum gates perform a series of complex tasks: they prepare qubits, entangle them to establish quantum connections, manipulate their probabilities through precise operations, and finally measure the results to extract useful data. This allows quantum computers to perform intricate calculations that are beyond the reach of conventional computers.

According to Hayes, quantum computers, like those used by Quantinuum, shift from controlling electron flow with gates to managing individual atomic ions. These ions are meticulously positioned in a vacuum chamber quieter than most regions of outer space.

“A vacuum chamber has a pressure that's better than most regions of outer space,” Hayes said. “These individual atomic ions, float above the surface of a little golden microchip, about 71 millionths of a meter, 70 microns above the surface.”

The gold-encrusted chip is held in place by precisely tuned voltages applied to electrodes on the chip. This setup ensures the ions don't touch the surface but remain perfectly positioned for manipulation.

Quantum computers rely on laser pulses to control ions, moving them between memory and processor units and facilitating the interactions needed for computation. To read quantum information, a quantum computer shines a laser on an ion; if it’s in the 'one' state, it scatters light, which is then detected to reveal its state. The ability to manage these quantum gates and ions is what gives quantum computing its incredible potential.

For anyone concerned about ions escaping its vacuum, Hayes explained that if the information does escape, the system begins to behave less like a quantum system and more like a conventional one.

“So you have to race against time and do these calculations quickly enough so that the information doesn't leak out into the rest of the world until you're ready for it to leak out,” he said. “Eventually, you have to leak it out so that you get an answer, but you only want that to happen at the very end, or you do it in a very controlled fashion, where you just pull out one bit of information from one atom, and sometimes that can help you do things like error correction.”

To be able to control this process, Google, for example, is using a special superconductive metal operating at temperatures that are eight times colder than space, which is a far cry from a computer sitting on a desk. As a result, quantum computers are unlikely to be leaving the lab any time soon.

The quantum threat to encryption

One of the tasks the blockchain industry fears quantum computers will be put to is breaking the encryption surrounding networks like Bitcoin and Ethereum. Beyond blockchains, quantum computing could also threaten the security of the global financial system, top-secret intelligence agencies, as well as all the data on your phone.

While the El Capitan supercomputer is incredibly fast, experts say it would still take the supercomputer over 10 billion years to break Bitcoin's encryption; a quantum computer, however, leveraging qubits, could theoretically do it in under 10 minutes.

“If you took today's blockchain structure and 10 years from now's quantum computer, you can break the encryption that comes from making private keys from public keys,” Director of Quantum Enterprise Development at Classiq, Dr. Erik Garcell, told Decrypt. “RSA encryption, for example, is definitely going to be something that quantum computing will be able to break.”

RSA encryption, named after its creators Ron Rivest, Adi Shamir, and Leonard Adleman, is a widely used method for securing data. It works by using a public key to encrypt information and a private key to decrypt it, relying on the difficulty of factoring large prime numbers for security.

Based in Tel Aviv, Israel, Classiq was founded in May 2020 and develops software tools and algorithms for designing and optimizing quantum circuits and applications. In June 2024, the company teamed up with BMW Group and NVIDIA to use quantum computing to enhance mechanical engineering systems in the automotive industry.

While Bitcoin and Ethereum primarily use Elliptic Curve Cryptography, as Garcell explained, the premise of technologies like blockchain and cryptocurrency is based on the idea that certain problems are incredibly difficult for conventional computers to solve.

“We built the assumptions that if we build a problem that's so hard that it wouldn't be practical to break it unless you spent an impossibly long time—essentially until the end of the universe trying to solve it,” he said. “In practical terms, this assumes the problem is computationally infeasible to solve within any reasonable timeframe, making the encryption secure against attacks by conventional computers.”

“However, quantum computers can solve these problems much more efficiently, challenging the assumptions we built on,” Garcell added.

Should the blockchain industry be worried?

Hayes and Garcell agree that quantum computing will become a reality in the next ten years, a figure that aligns with an April 2024 report by digital consulting firm McKinsey Digital that said the chemicals, life sciences, finance, and mobility industries are likely to see the earliest impact from quantum computing and could gain up to $2 trillion by 2035

“Finance is probably going to see the most money out of this in the shortest amount of time because they're the most sensitive to any small advantage computationally,” Garcell said.

Big banks are diving into quantum computing to transform finance. Wells Fargo started collaborating with IBM and MIT in 2019, JPMorgan Chase teamed up with Quantinuum in 2020, and Goldman Sachs began exploring quantum computing with QC Ware in 2021.

While the blockchain industry anticipates the coming quantum apocalypse, according to Garcell, cracking Bitcoin’s encryption may not even be on quantum computer developers' list of objectives. Instead, Garcell believes developers may use quantum computers to mine Bitcoin.

“People want to make money. So a lot of people are going to be mining this stuff, and that whole system needs to figure out a way that's a little bit harder for a quantum computer to do,” Garcell said. “With these are harder calculations, you might need a quantum computer to mine the Bitcoin of the future.”

Garcell did acknowledge that while there is a financial incentive not to try to take down the Bitcoin network, he said the blockchain industry needs to be ready for when quantum computers become mainstream.

Quantum computers could break cryptographic systems but also enable stronger encryption. To address this, blockchain developers are planning upgrades to resist quantum attacks.

“You’ve got to keep adapting, and blockchains must evolve to counter new threats and vulnerabilities,” Garcell said.

To Garcell’s point about evolving views on quantum computing, in 2019, Ethereum co-founder Vitalik Buterin suggested that quantum computers, such as those from Google, IBM, and Microsoft, were largely experimental. However, three short years later, in 2022, Buterin said that quantum computers could break certain encryption methods like RSA and elliptic curves, core components of many cryptographic systems.

In March, Buterin floated the idea of a hard fork to safeguard the Ethereum blockchain against quantum computer threats. The plan involves reversing blocks after an attack, pausing certain transactions, and adding quantum-resistant validation methods.

The future of quantum computing

Even if blockchains are safe for now, the crypto world is not taking any chances. Quantum-resistant blockchains like the Quantum Resistant Ledger (QRL), Praxxis, and QAN are already being developed in preparation for the potential quantum apocalypse. We can rest assured knowing—even if quantum computers start taking over the world—our crypto will be safe.