In the previous article, I explained the reason why quantum computing is interesting and I simply explained how they’re conceptually different from traditional computers. Recently, I have been wondering how hardware could change when it comes to Quantum computers, so I tried to find answers for this question. In this article I will try cover the difference I found and give some technical details about hardware differences.
For instance, a computer is essentially made of:
- Motherboard (main board with circuits and electrical CMOS transistors)
- CPU
- Storage (HDD)
- Ram
- Network card
- Graphics card
- Power supply
- Eventually all ports with I/O accessories (monitor, keyboard, mouse…etc)
(This is a very simplified summary of main components found in our PCs)
Common concepts:
- Storage is measured in (mega)bits/bytes.
- Network transmissions is measure in (mega)Bits/bytes Per Second.
- CPUs are made of multiple cores with their performance measured by their frequency (in Hz/GHz). This means the processing speed is a few billion simple logic operations per second.
- Evolution is limited by Moore’s law.
If we’re ever to turn to Quantum computers how will these concepts
change?
Here are some answers (as far as we know at the time of writing):
Please note that quantum computers we have at the moment are usually hybrid, which means we use their computational power in conjunction with a classic computer. They are not meant to replace Classical computers and therefore we don’t really have a classical component Vs. Quantum component for each item. However I will cover what makes a Quantum computer (in the widely used Hybrid model like IBM’s machines)
Quantum computers are made of:
- Main board with SQUID – “a quantum transistor”
- QPU (quantum processing unit), AKA co-processor.
- No Storage: By its nature, you can’t save or duplicate information on a quantum computer. There is some work on quantum hard drives and there are workaround involving using DNA or converting qubits to bit and store them on regular HDD.
- No RAM: During calculations the qubits themselves hold the data required. There is the qram concept but I could not find any proofs that is being used in practice in current QCs.
- Network card: Current (hybrid) Quantum Computers are not networked and they communicate through the paired classical computer. Quantum networks via fiber links as a medium are currently a possible solution. This topic is highly active in the QC research field!
- No Graphics card: quantum computers are mainly used for calculations. You’re not going to play games watch videos on them. They’re not designed to perform such tasks. The classical part takes care of that.
- Power supply: it differs a bit from the classical one, but it still runs on normal electricity to power the cooling system.
- I/O is managed by converting them from/to binary through quantum measurement (The Quantum processors we currently have are always used along with a classical computer to control them.)
Differences from the common classical concepts:
- Storage is measured in quantum bit qubit (aka: Qbit – the equivalent of bit).
- I could not find enough information on quantum networks speed measurements. Afaik, the existing QCs are not directly connected to internet and there is no information regarding the efficiency of a network between two connected quantum computers in the experiments I found in Delft and tum. I am not aware of 2 distant Quantum computers that have been directly connected.
- To compare performance, we can’t talk about GHz anymore. However, we need to compare efficiency in terms of time-complexity. The processing power of QCs is measured in teraflops – rate of flipping (trillions of logic operations per second). Each QPU has a finite number of qubits. The more qubits the faster its performance. The fastest I heard of is 2000 Qubits computer. (not universal)
- Quantum computing still can’t break Moore’s law, since it is a law about transistors in a dense integrated circuit. Therefore, the law does not even apply to Quantum computers (QCs) and thus QCs are not affected by it. However, another law exists for QCs, it’s called rose’s law.
Some information about quantum storage technologies:
- https://www.tomshardware.com/news/quantum-computing-news-data-drive,38038.html
- https://www.wired.com/2017/03/quantum-computers-used-hard-drives-made-dna/
In order to find the answers I was looking for and write this article I had to read some resources, here’s the list:
- https://www.dwavesys.com/tutorials/background-reading-series/introduction-d-wave-quantum-hardware#h2-9
- https://www.nap.edu/read/25196/chapter/7#130
- http://quantumly.com/quantum-computer-speed.html
I hope you liked my article! I’m thinking on writing my next article on Quantum networks and quantum cloud computing. I’m always wondering what happens if we host websites on quantum computers? How can quantum computers revolutionize the web? Is such a thing possible or useful? Maybe I will gather more information and write my next article to talk about that (spoiler: remember we said quantum won’t replace classical) 🙄