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[2018 oracle code one] how to program a quantum computer

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You’re thinking too classically – how to program a quantum computer
Speaker: Tim Ellison
IBM

For more blog posts, see The Oracle Code One table of contents

General

  • When reach maturity of computers have today, will significantly outperform today’s classical computers
  • Need quantum computer to model quantum mechanics

Classical computers

  • Classical data and logic representation – data encoding (binary/ascii), logic gates (binary), computing circuits (built out of logic gates)
  • Need resilient bit store, data representation and algorithms. Don’t think about it much because data is reliable
  • Some problems are hard/not a good fit
    • Traveling salesman – 10 cities is 1.8 million routes. 20 cities is 1 billion billion routes
    • Optimizations (ex: minimize wastage cutting wood)- requires starting with a guess and trying all options
    • Modelling molecutes (simulate electron interactions – 25 electrons is laptop sized problems. 43 electrons ins Titan supercomputer
    • Modeling caffeine is impossible on today’s computers. But could represent in 160 quantum bits. And pharmaceuticals are far more complicated.

Quantum

  • Qubit in both 0 and 1 state at same time. Superposition
  • Collapses to a value when observe.
  • Can influence probability of it being a 0 or 1
  • Combine qubits to cause correlation of random results. Quantum entanglement “causes” both “linked” qubits to git save values.
  • Call experiments (vs programs) for quantum because results not deterministic
  • Power doubles every time add qubit.
  • 275 qubits is more states than number of atoms in universe
  • Fast to factor prime numbers using Shor’s algorithm [watch out security!]
  • Expect quantum computers to be used – chemistry, AI (classification, machine learning, linear algebra), financial services (portfolio optimization, scenario analysis, pricing)
  • Built with ions, photons, superconducting circuits.

Demo

https://quantumexperience.ng.bluemix.net/qx

  • 5 qubits
  • Get 21 units (since free, it is rate limited.) Once experiment completed, get results back
  • Can run on real quantum computer or on simulator
  • Result gives you the probability of different results
  • Shows openqasm. A quantum assembly language
  • H gate puts into superposition state
  • Large program runs in O(square root of n) vs O(n^2) complexity

Resources

  • Python API: https://github.com/QISKit – build, compile/transpile and execute
  • Run experiments: https://quantumexperience.ng.bluemix.net/qx

Journey

  • Science is well understood
  • Machines currently error prone. Nothing can do on quantum that can’t do on classical (yet)
  • Quantum Advantage – being able to benefit from quantum
  • Prediction: less than 5 years for chemistry. 10-15 years for breaking cryptography
  • Starting to build data centers in Poughkeepsie (upstate NY)

My take: The basics of this I’ve heard before. It was cool seeing IBM’s experiment generator used. It’ll be interesting seeing where this goes. The speaker said this was normally a 2 hour talk. I liked the part about applications of quantum and how they are built. I also liked seeing the assembly and graphical code.