The Qubit – The Building Block of the 1st Quantum Computer
The quest to build the world’s first quantum computer continues. Tech heavyweights such as IBM, Microsoft, Google and Intel breathlessly tout every tiny, incremental step forward.
In 2009, physicists at NIST made the first small-scale device that could be described as a quantum computer. It used ultracold ions to demonstrate separately all the steps needed to perform quantum computations.
What is a Qubit?
A qubit is the fundamental building block of a quantum computer. Traditional computers store and process information in binary states – either ones or zeroes – but quantum computers can use qubits that are in superpositions of both states at the same time, giving them a massive leg-up in computing power.
To create a qubit, scientists suspend an electron in an electromagnetic field and control its spin state. A spin that is parallel to the field is interpreted as a 1, while an antiparallel spin is a 0.
Atom Computing claims to have built the first quantum computer with more than 1,000 qubits. The company’s chip, dubbed Condor, has 1,121 superconducting qubits arranged in a honeycomb pattern and is expected to be available for commercial customers next year. The company is also releasing Heron, the first of a new flock of modular quantum processors that could lead to computers with millions of qubits. But it will take years before the technology reaches mainstream use.
How does a Qubit work?
In a regular computer, each bit can be in only one state at a time (like trying one corridor at a time in a maze). But a quantum computer stores information in superposition. That means it can try every possible pathway in the maze all at once.
To make a qubit, researchers must create a system in which the electron’s magnetic spin can be manipulated independently of its other properties. Atomic nuclei are one such system. By applying radio frequency pulses, researchers can orient the spin of a nucleus in a particular way (either parallel or antiparallel to an external electromagnetic field) to form a quantum bit.
Another possibility is to use trapped ions, which can also attain a quantum state with the help of electromagnetic fields and lasers. But building large numbers of qubits that can maintain their coherence at room temperature is a challenge. Moreover, there is the risk that they might interact with each other, which degrades their accuracy.
What are the limitations of a Qubit?
A qubit is the basic unit of quantum computing. A quantum computer is capable of performing certain tasks that are impossible to perform on a classical computer, such as finding the prime factors of a number or solving an algebraic equation.
However, there are many challenges to constructing and operating a quantum computer. It is important to maintain coherence between qubits for long enough to run an algorithm. It is also essential to find ways to detect and correct errors. Finally, it is crucial to develop methods for measuring a quantum system without disturbing its state.
Scientists have created several types of quantum computers. One type involves entangled molecules. For example, scientists at IBM’s Almaden Research Center used four ionized beryllium atoms in an electromagnetic trap. Each ion had a parallel spin, representing a 1, and an antiparallel spin, representing a 0. These two states were superimposed on each other to form a qubit. The atoms were then manipulated using radio-frequency pulses to execute an algorithm and measure their final states.
What are the potential applications of a Qubit?
Scientists are working to build machines that exploit the strange properties of the atomic world to make calculations much faster. They say quantum computers could crack cryptographic systems used to secure data, speed up drug discovery, find new materials and improve machine learning.
The key hurdle is making a qubit computer that can operate reliably without any interference from its surroundings. This requires keeping the computer cooled to near absolute zero, which is not easy. It also requires a special laser to control the electron’s spin state, and a vacuum or cryogenic chamber to keep it isolated from its environment.
Companies like IBM and Rigetti are working on such quantum machines. But it’s not clear when they will be useful to businesses and other scientists. One approach, called quantum annealing, uses multiple qubits to solve optimization problems at scale. It has potential applications in logistics and finance. But it’s still a prototype that works only for certain mathematical problems.