That is why it is perhaps not easy to appreciate fully the importance of quantum supremacy, which a US technology giant and a Chinese university claim to have achieved in 2020. The challenge is broadly defined as using quantum computers to solve problems that today’s computers cannot.
These were two highly contrived experiments – respectively, calculating the randomness of a series of numbers and checking the distribution of photons – that may seem no more useful to us than managing to stay in the air for a matter of seconds must have appeared in 1903. They do, however, bring us slightly closer to a future, perhaps 10 or 15 years away, when quantum information science looks likely to open many new opportunities.
Now is the time to start preparing for the disruption, and, with this in mind, here are five things that everyone should know about quantum computing.
1. Quantum computers work differently
Traditional computers currently store data using bits. They have two states – either on or off – represented as a 1 or a 0. Quantum computing replaces binary bits with qubits, which have more states that change continuously. Qubits can be on, off or somewhere in between all at the same time. This state is called “superposition” and enables qubit-based computers to carry out far more calculations, much faster.
2. Today’s quantum computers are unreliable
Major corporations and some universities are already investing millions to buy or develop their own quantum computers. Many more are benefitting from cloud-based quantum computers.
For the time being, however, quantum computers are prone to errors because qubits are highly sensitive to external 'noise'. Qubits only function “coherently” when they are cooled down to mere thousandths of a degree above absolute zero, which also protects them from the destabilizing effects of radiation, light, sound, vibrations and magnetic fields. All of this limits the size and complexity of problems that quantum computers are currently able to tackle.
3. There are two kinds of quantum computing
Gate-based quantum computing works in much the same way as traditional computing. A transistor performs a Boolean function: a sort of binary logic, commonly seen in advanced search engines, that works with modifiers such as ‘AND’ or ‘NOT’. The transistor receives two incoming signals and depending on what it encounters, sends out a new electric signal. In the quantum model, qubits replace the transistors.
Computers based on quantum annealing take a radically different approach. Quantum annealers run adiabatic quantum computing algorithms. Instead of allowing the entanglement of all qubits, they create an environment where only restricted, local connections are possible. When they attain superposition, they can be used to mediate and control longer range coherences. This makes them suitable for a much narrower range of tasks, such as solving optimization problems – i.e. choosing the best solution from all feasible solutions. They currently sell for around $10 million.
4. Quantum computers will disrupt cyber security
Quantum computers will be powerful enough to decipher the encryption codes that currently protect all our sensitive data, from mobile banking to medical records. That is why scientists are urging governments and organizations to start exploring and implementing quantum encryption systems now.
Wikipedia defines quantum cryptography as “the science of exploiting quantum mechanical properties to perform cryptographic tasks”. It is based on the behaviour of quantum particles, which are smaller units than molecules. For example, an encryption system called quantum key distribution (QKD) encodes messages using the properties of light particles.
The only way for hackers to unlock the key is to measure the particles, but the very act of measuring changes the behaviour of the particles, causing errors that trigger security alerts.
5. Standardization work is underway
IEC and ISO have set up a working group (WG 14) in their joint technical committee on information technology (JTC1) to identify the standardization needs of quantum computing. It is hoped that their work can support the evolution of quantum computing by paving the way for a foundation of common vocabularies and best practices. This should enable developers to focus their attention on higher-level challenges, rather than starting their projects from scratch.
Quantum cryptography is an area of interest for two key expert groups: