In conventional computing, the use of CMOS (Complementary Metal Oxide Semiconductor) technology as the foundational circuitry for digital logic gates in CPUs has become the industry norm. CMOS's remarkable success can be attributed to its impressive qualities of high noise immunity and low power consumption. In quantum computing, the possibilities are diverse, with potential hardware choices basing on electrons, photons, atoms and trapped ions etc. Quantum computers harness the principles of superposition and entanglement within pairs of these entities. The question at hand is whether there is a definitive preference in these various hardware options or if the quantum computing hardware landscape remains undecided. Is there a consensus regarding the ideal quantum computing hardware, and if so, what factors contribute to its standing as the preferred choice?"
The short answer is the field is very much undecided.
The longer answer is the ideal quantum computing hardware is whatever can run a useful quantum algorithm that solves a classical intractable problem (e.g. Shor's algorithm to break current RSA encryption). That means the field is trying to find quantum computing hardware which can scale to have the requisite number of qubits to run such an algorithm, and that qubit number is also set by how close to error-free they are (with noisy systems requiring more qubit overhead for error correction). There are a few different schools of thought for how to scale that different companies are trying with different platforms.
- One approach is incrementally increasing the number of qubits. IBM is building chips with more superconducting qubits on each one, and then wants to link them together to slowly the build the number up from a few, to tens, to hundreds (where they're at now) to thousands (their goal for the next few years)
- Another approach is developing a qubit that's (theoretically) easier to scale quickly. Intel is working on semiconductor-based quantum dots, because they know semiconductor fabrication and scaling better than anyone, so they'll catapult ahead if they their qubit realization lets them utilize their existing know-how
- Another is to bet on new science to enable new platforms with favorable properties for scaling. For example, Microsoft is working on Majorana fermion-based quantum computing which should innately be more fault-tolerant than the current state of the art, but they still need to nail down some of the underlying physics.
That's just a couple of points from some of the big US companies in the field, but there are plenty of other large companies and start-ups trying to figure out how to scale a bunch of developed and nascent qubit platforms because at the end of the day, we need orders of magnitude more qubits to get to large-scale quantum computing and no one is sure how we'll get there.