What is a Quantum Computer?
Quantum computers have the potential to solve certain types of problems faster than classical computers. For example, they could eventually be used to solve optimization problems, simulate quantum systems, or even factor large numbers, although they can’t do that yet.
But how does it work?
In contrast to classical computers, quantum computers use the principles of quantum mechanics to perform certain types of computation more efficiently. It is important to note that, while classical computers store and process information using bits, which can be either 0 or 1, quantum computers use quantum bits, or qubits, which can exist in a superposition of 0 and 1.
In a quantum computer, qubits, which represent and manipulate information in a quantum state, are the basic building blocks. Unlike classical bits, which can only exist in one state at a time, qubits can exist in several probabilistic states. Quantum computers can perform simultaneous parallel computations over a large number of possibilities thanks to this property.
Quantum computing also relies on the concept of entanglement. In entanglement, two or more qubits correlate in such a way that the state of one qubit is affected by the state of the other, regardless of the fact that the two are physically separate.
Top 5 Types of Quantum Computers
Currently, there are several different approaches to how quantum computers are developed and produced. All examples of companies listed are incomplete. As we speak, the five leading qubit type approaches are:
One of the most popular types of quantum computers is the superconducting qubit quantum computer. Usually made of superconducting materials, these quantum computers use tiny electrical circuits to generate and manipulate qubits. When using superconducting qubits, gate operations can be performed quickly.
Companies actively researching and building superconducting quantum computers include Google, IBM, IQM, and Rigetti Computing.
This type of quantum computer uses photons (particles of light) to carry and process quantum information, and there are some nuances and complexities to how this works, which Richard Murray — CEO of photonics-based ORCA Computing — explains here in an exclusive interview with The Quantum Insider. For large-scale quantum computers, photonic qubits are a promising alternative to trapped ions and neutral atoms that require cryogenic or laser cooling.
There are dozens of companies working with photonic quantum computing technology. Some of them are Xanadu, ORCA Computing, Quantum Computing Inc and PsiQuantum.
Photonics is a very good example of how photonics is a general category used to incorporate quantum computers. Xanadu’s “squeezed light” approach differs materially from PsiQuantum’s, for example.
3. Neutral Atoms
Quantum computing based on neutral atoms involves atoms suspended in an ultra-high vacuum by a tightly focused array of laser beams called optical tweezers, although not all neutral atom companies use optical tweezers. Neutral atomic quantum computers are less sensitive to stray electric fields, which makes them a good choice for quantum processors.
Companies working with atomic neutral (cold) quantum computing technology include Pasqal (merged with Qu&Co), Atom Computing, ColdQuanta, and QuEra.
4. Trapped Ions
An ion trapping quantum computer involves using atoms or molecules with a net electric charge known as “ions” that are trapped and manipulated using electric and magnetic fields to store and process quantum information. Because trapped ions can be isolated from their environment, they are useful for precision measurements and other applications that require a high degree of stability and control. Also, qubits can remain in a superposition state for a long time before becoming decoherent.
Representing the community of ion companies trapped in quantum space, we have Quantinuum (a company born from the merger of Cambridge Quantum Computing and Honeywell Quantum Solutions), IonQ, Quantum Factory, Alpine Quantum Technologies, eleQtron, among others
5. Quantum Dots
Quantum dot computers use silicon qubits which are made up of pairs of quantum dots. In theory for a quantum computer, such ‘paired’ quantum dots could be used as powerful quantum bits, or qubits.
Companies that focus on this area include Diraq, Siquance, and Quantum Motion.
6. Another Approach
Other alternatives for building workable quantum computers include electrons on helium, NV diamond, and topological approaches.
When Can We Expect the Rise of Commercial Quantum Computing?
Experts in the field predict that as quantum computing technology advances, the cost of quantum computing hardware will continue to decrease over time, making it more affordable for businesses and a wider range of organizations. The price of a quantum computer is likely to be influenced by several important factors, including how advanced inventions in the sector are made, market demand, and competition among quantum computing companies.
As for technological advances, the most advanced quantum computers currently available from companies like IBM and Google have hundreds of qubits. It may be necessary to increase the qubit number to thousands or even millions to have any meaningful commercial impact with this technology.
One obvious barrier to making progress is that some quantum computers, for example, superconducting quantum computing, require complex cooling systems to keep the qubits at low temperatures to operate properly, as well as reliable error correction systems. Problems like these create scenarios where there is no set timeframe for when quantum computers will become commercially available, although many industry thought leaders are betting that practical applications for the technology will emerge in the next ten to twenty years.
Quantum computers require expertise across physics, engineering, and computer science. The approaches discussed above all have advantages and disadvantages, and each is the subject of ongoing research and development. In order to build a quantum computer, one must consider a number of factors, including the specific problem that needs to be solved, the resources available, and the advances in technology at any given time.
To conclude, we must turn to the experts in space, John Preskill, Caltech faculty member and the Richard P. Feynman Professor of Theoretical Physics and Allen VC Chair of Leadership and Lenabelle Davis for the Quantum Materials and Information Institute, who interviewed in 2022 by Caltech Science Exchange. On how long we have to wait for a quantum computer to do something useful, his response was candid:
“Well, it depends on what you want. We are in the early stages of developing quantum computers, but even now, from a scientific standpoint, the quantum computers we already have are empowering. They will allow us to explore the behavior of complex quantum systems in ways we have never done before, and that will fuel scientific discoveries over the next five or 10 years. But for widespread practical impact, I think a reasonable estimate is decades or more than 10 years.”
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Featured image: Chip ion traps for quantum computing at NIST.