Quantum gates: what is the hardware?

[nomadreid]

In looking up "quantum gates", e.g. "Hadamard gate", all I come across is the matrix representations of the operations. But I do not see how, physically, they are achieved. (I also presume it will be different if we are talking about photons or electrons.) Could someone give me an appropriate link? (If you want to concentrate on a single one, then pick the Hadamard.) Thanks.

 

[DrClaude]

You should use Google scholar. Here's one example: http://link.aps.org/doi/10.1103/PhysRevA.84.050301

 

[nomadreid]

Thank you, DrClaude. Good advice. However, I should have put "freely accessible articles" in my request: in your example (and most of the other examples from Google Scholar), I get the abstract but not the article unless I want to pay. (I have had the experience before of paying for an article and not finding it what I wanted, so I wish not to repeat this. Or just think of me as a cheapskate.) I tried ArXiv, but again I come across the gates being black boxes.

 

[bp_psy]

Search harder.
http://arxiv.org/abs/1107.0822

 

[nomadreid]

Thanks, bp_psy. That is much better. I deserve a tongue-lashing for overlooking that.

 

[f95toli]

There are LOTS of different ways of making quantum gates. The systems can be everything from solid state (semiconductors, superconductors) to individual ions to photons in a fibre.

 

[nomadreid]

Thanks, f95toli. The more the merrier. All suggestions for finding specifics are welcome.

 

[bp_psy]

Quantum dots are pretty cool.
http://www.ohio.edu/people/diao/papers/qd.pdf

 

[Zarqon]

There are many different approaches to implementing quantum hardware, below I mention a couple of approaches so that you have some words that you can google. If you're just learing about them, I would say something simple like wikipedia is probably better than real research articles to start with, though some review articles might be good as well.

Some approaches:

• Ion traps
• Superconducting qubits (squids)
• NV-centers in diamond
• Impurities in crystals (like rare-earth ions)
• QC in Linear optics
• Quantum dots
• Cold gases (BEC) or hot vapors (for quantum memories)