2018-06-13

Okay, a week or so but some interesting stuff.

I've started a collection of the interview problems I've been given. I've gotten through most of them (I think) in the interviews but they're fun to polish up and have around to think about. I'm doing them in both C++ and Go, I've got the first one done (and fixed a bug my interviewer and I didn't realize I had), so that's cool.

On to the more interesting stuff: quantum computing. I'm reading Quantum Computing for Computer Scientists; the nice thing about this book is that it opens with two chapters on the pre-requisite math. Between that and Maths for ML, I'm getting a good handle on the linear algebra I need to move forward with my skills. My quantum computing book shelf is slowly growing...

As for programming quantum... things..., I've been toying with the Microsoft Quantum SDK and pyQuil simulators, though I've only written a simple entanglement demo:

        program bell is
                ones, zeroes, agree ← 0
                repeat 1000x:
                        qubits[2]
                        H(qubits[0])
                        CNOT(qubits[0], qubits[1])
                        measure(qubits)
                        increment ones if qubits[0] is 1 otherwise increment zeroes
                        increment agree if qubits[0] == qubits[1]
                expectations:
                        ones ≈ zeroes
                        agree = ones + zeroes

I think I understand how this works:

  • the Hadamard gate puts the first qubit into a state of superposition
  • the second qubit is initialised to zero
  • the CNOT gate toggles the second qubit only if the first qubit is 1

This is sort of a weak entanglement, but it does tie the value of the second qubit to the first.

I'm still on the second chapter of the QC for CS book ("Complex Vector Spaces"), but I'm making steady progress.

Still ahead on the CS course, too --- I was able to get a lecture or two in Monday morning, and I anticipate getting some done tonight. Or maybe I'll do more maths. Probably maths, if I'm being honest... I will say that the CS course was surprisingly useful during some of my interview questions, so I'm interested to see how it makes me a better programmer and engineer overall.


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