Quantum Computers: Why They Are Hard To Build — And Worth The Effort (2024)

FAQs

Why is it so difficult to build a quantum computer? ›

Using qubits in computers is incredibly difficult. Qubits are extremely sensitive to noise and hold their quantum state typically for very short periods, Lipman pointed out. He said the largest quantum computers currently available consist of only a few hundred noisy physical qubits.

The three main challenges we'll look at include quantum decoherence, error correction, and scalability. Each is a major hurdle on the road to quantum computing, and must be overcome if the technology is to reach full potential.

Quantum computers are extremely sensitive to noise and errors caused by interactions with their environment. This can cause errors to accumulate and degrade the quality of computation. Developing reliable error correction techniques is therefore essential for building practical quantum computers.

Quantum mechanics is deemed the hardest part of physics. Systems with quantum behavior don't follow the rules that we are used to, they are hard to see and hard to “feel”, can have controversial features, exist in several different states at the same time - and even change depending on whether they are observed or not.

Most quantum programming languages today still resemble assembly language, stringing together low-level operations, without mindfulness towards things like data types and functions, and what's typical in classical software engineering. “Quantum computers are error-prone and difficult to program.

Quantum error correction

Arguably, one of the biggest issues in current quantum computers is the fact that they are unreliable and prone to calculation errors. These machines and their quantum bits – qubits – are so sensitive that various disturbances can lead to errors in their calculations.

For a while researchers thought they'd have to make do with noisy, error-prone systems, at least in the near term.

Real-time control. Not having any ability for I/O of any sort, a quantum computer has no capability for controlling real-time devices, such as process control for an industrial plant. Any real-time control would have to be made by a classical computer. Media playback or recording.

The scientists' results show that classical computing can be reconfigured to perform faster and more accurate calculations than state-of-the-art quantum computers.

Can quantum computers do anything useful yet? ›

Researchers have yet to make prototype quantum hardware do anything practical, although they have demonstrated prototype machines that can solve a commercially useless math puzzle faster than a state-of-the-art supercomputer.

Future quantum computers could open hitherto unfathomable frontiers in mathematics and science, helping to solve existential challenges like climate change and food security.

As of 2022, they predict to have over 1000 qubits by 2023, and 1 million qubits in 2030. Google even thinks of building a 1M qubit device by 2029. Unfortunately, such claims often cannot be found on the manufacturer's websites, but are taken by journalists from talks and presentations.

Over the years, experimentalists have constructed small-scale quantum computers using trapped ions and superconductors. In 1998, a two-qubit quantum computer demonstrated the feasibility of the technology, and subsequent experiments have increased the number of qubits and reduced error rates.

By most estimates, a single qubit costs around $10K and needs to be supported by a host of microwave controller electronics, coaxial cabling and other materials that require large controlled rooms in order to function. In hardware alone, a useful quantum computer costs tens of billions of dollars to build.

Quantum computers have shown that they can process certain tasks exponentially faster than classical computers. In late 2019, Google claimed that it had managed to solve a problem that would take 10,000 years for the world's fastest supercomputer within just 200s using a quantum computer.