*Not so long ago, the limitations of classical computers pushed scientists to develop a new type of computing – quantum computing. Quantum computers use qubits instead of classical bits and can perform certain calculations much faster than classical computers. This advantage can potentially transform numerous spheres and make our life better. In this article, we’ll provide an overview of quantum computing, including industries and fields that could be revolutionized by quantum computing. We will also discuss the challenges and risks associated with this technology, as well as what the future holds for it.*

Interior of an IBM Quantum computing system. (Credit: IBM)

## What is Quantum Computing?

Computing has come a long way since the quantum theory was developed in the 1920s and the first programmable computer, the Electronic Numerical Integrator and Computer (ENIAC), was built in 1945. The machine was the first*"automatic, general-purpose, electronic, decimal, digital computer,"*according to Edwin D. Reilly's book "Milestones in Computer Science and Information Technology". What exactly is quantum computing? In brief, it’s a rapidly-emerging technology that harnesses the laws of quantum mechanics to solve complex problems in a more efficient and powerful manner than classical computers.

*For some problems, supercomputers aren’t that super.*At its core, quantum computing relies on the use of quantum bits (qubits) to process and manipulate information. Unlike classical bits, which can only exist in one of two states (0 or 1), qubits can exist in multiple states simultaneously due to the phenomenon of superposition. This allows quantum computers to perform many computations simultaneously. Another key principle of quantum computing is entanglement, which allows qubits to become correlated in such a way that the state of one qubit can instantaneously affect the state of another, even if they are physically separated. This allows quantum computers to perform certain tasks much faster than supercomputers – factoring large numbers, searching through large databases, etc.

## How Do Quantum Computers Work?

As just mentioned, quantum computers use qubits instead of bits to run multidimensional quantum algorithms. Qubits are created using superconductors, which exhibit quantum mechanical effects such as Cooper pairs that can carry a charge through insulators via quantum tunneling. The behavior of qubits can be controlled and manipulated by firing microwave photons at them. Qubits can be placed in a state of superposition, representing a combination of all possible configurations of the qubit. Groups of qubits in superposition can create complex computational spaces that can represent complex problems in new ways. Quantum computers are smaller and require less energy than supercomputers but need to be very cold, which is achieved using super-cooled superfluids.## Current State of Quantum Computing

Quantum computing is a rapidly evolving field that is going to revolutionize the way of solving complex problems. Several companies, including IBM, Google, and Rigetti, have already built quantum computers and utilize them. These computers range in size from a few qubits to over 100 qubits, and each has its own unique architecture and set of capabilities.- In 2017, Rigetti announced the public beta availability of Forest 1.0, the world’s first full-stack programming environment for quantum computing.
- Google’s Sycamore is a quantum processor that has 53 qubits. It was developed in 2019 and claimed to complete a task in 200 seconds that would require a high-end supercomputer 10,000 years to finish.
- IBM Quantum System One quantum computer was introduced by IBM in 2019 as well. It contains a 20-qubit transmon quantum processor that is housed in a 2.7x2.7x2.7 meter computing system. Interestingly enough, IBM announced the new 433-qubit 'Osprey' processor on the IBM Quantum Summit 2022.

*"The new 433 qubit 'Osprey' processor brings us a step closer to the point where quantum computers will be used to tackle previously unsolvable problems,"*– Dr. Darío Gil, Senior Vice President, IBM and Director of Research. In addition to hardware developments, software tools for quantum computing are also advancing. Programming languages such as Q# and Qiskit allow developers to write quantum programs and run them on quantum hardware or simulators. However, quantum computing still faces some challenges and limitations. The major one is error correction. As a quantum program runs, errors quickly accumulate, posing challenges for scientists. So, developing effective error correction methods is crucial for building large-scale, reliable quantum computers. Another significant limitation is scalability. While quantum computers with tens or hundreds of qubits already exist, building a large-scale quantum computer with thousands or millions of qubits is still a challenge. However, there is optimism that these challenges will be overcome in the coming years, paving the way for wider adoption of quantum computing. IBM Quantum systems promise to scale up towards 4,000+ qubits by 2025 and beyond.

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