Posted on September 9, 2017 9:29 am

Do quantum computers have traditional computer parts?

So, at this point it is hard to say that current quantum computers (well more like chips) have integrated within them RAM (random access memory), ROM (read only memory), hard drives (another memory component), and buses or data lines — but there are developments in quantum computer architectures, with most of them being quantum-classical hybrid architectures, where you certainly do have components that manipulate qubits or qudits (so hot right now) to carry out calculations on quantum circuits (like a processor), schemes to store this information onto other qubits (memory), and then also systems to carry out measurements after our manipulations to get the result of our quantum informatical computation (with quantum information relayed through optical buses).

What are quantum computers/chips (or just qubits) usually made out of currently? Well it’s like the Cambrian Explosion (ok, maybe not that diverse) but with different quantum computing architectues or substrates if you will — each with their advantages and disadvantages.

Trapped ion qubits, superconducting circuit qubits, diamond nitrogen vacancy qubits are some examples of physical representations or realizations of qubits — generally you can use something as a qubit as long as you can manipulate the state of said quantum entity (electrons, photons ~ usually spins in which case, some other field quantity, etc) in a two-level (so you get the 0 or 1 state or superpositions of these) or multi-level (qudits can take on these multi-level states, so think 0, 1, 2 … n-states) fashion.

You usually end up manipulating these quantum states using optics, so photons, or different electromagnetic frequencies such as microwaves or radio-frequency waves — and often in composite pulses (there are experimental benefits to doing this where delivering our manipulations in pulse sequences offers robustness to noise or other errors as opposed to a single pulse).

Another aspect of current quantum computing hardware you may be familiar with is the near universal requirement for cryogenic temperatures (from balmy and warm 1~10 Kelvin to colder milli-Kelvin to even colder micro-Kelvin temperatures) as well as pulling a hard vacuum for certain qubit modes (notably trapped ion methods).

And the field really is rapidly marching forward with centers in the US, Europe, Australia (these three nations are heavily invested in bringing forth a working universal quantum computer), Asia (China focuses heavily on quantum informatic experiments, Japan and Korea also have their sights set more on quantum information manipulation with quantum optical systems).

In fact there are proposals to build a “football” sized quantum computer based on trapped ion methods — owing to their good entanglement lifetimes, scalability and straight forward manipulation and addressing of qubits (trapped ions are also a pretty legacy technology, used in things like atomic clocks or as components in mass spectrometry work flows) — this is pretty exciting and would actually be a great thing to invest in and make it a big public science project much like how CERN’s LHC or the LIGOs might be operated and used.

You can obviously see where this would be a good first step but might need improvement to break the mainstream commercial barrier — the intense energy costs of pulling a hard vacuum and maintaining milli- to micro-Kelvin temperatures (maybe you can do some clever thermal engineering and integration to save some money but the operating costs will still be steep).

Nonetheless it would be a wonderful undertaking and could prove valuable in guiding the design and development of future quantum devices (maybe with the bulky and expensive quantum computer you can figure out how to build a more compact and energy efficient/heat-resistant one).