Measuring a qubit

Explains how to extract information from a qubit. Part of a series on "Quantum computing for the determined". The full series is at: http://www.youtube.com/user/mnielsencourses?feature=mhum#p/c/1826E60FD05B44E4

Category:

Science & Technology

Tags:

• quantum
• qubit

[mnielsencourses]

@goldenshale - there's a more general notion of measurement, which you can build up by combining (perhaps in a very complicated way) single-qubit measurements and unitary operations. I describe some explicit examples later, e.g., in the video on distinguishing quantum states.

[annelics]

"Alpha and beta are now gone."

I teared up.

[jestery]

This notation bothers me a bit :( The measurement gate looks like an AND with only one input. And why not use the classic NOT symbol for the quantum NOT gate (even with an X inside)?

[goldenshale]

Can you explain what you mean when you say that in effect you can "simulate an arbitrary quantum measurement?" Does that mean you are building distributions for alpha and beta by taking samples? Do you have to perform all of the quantum operations again to recover the state for each measurement, or is there a way to copy a qubit?