Quantum computing

• superconducting - google, ibm
  • cool temperatures, small chip - box = interface between quantum and normal interface
• photonic
  • doesn’t need to be cooled down, photons are cool
• trapped ion/atom
  • ions are indistinguishable
• not faster (clock speed) - more efficient - run different algorithms
• new complexity class BQP
  • bounded-error quantum polynomial time
  • travelling salesman problem
  • constructing time table for school
• quantum mechanics, only allow unitary operations
  • reversible and
• quantum and classical register
  • after the of algorithm, can only read classical register

Shor’s Algorithm (factorization)

• to find factorization you can use/find period -> fourier transform

Parametrised quantum circuits

• check which gates can be implemented efficiently, then use them

• What are the expected advantages of quantum computers?

• How one can program quantum computers (and their simulations)?

• What is quantum supremacy and how far are we with it?

Quantum supremacy is solving practically unsolvable problem on classical computer (too much time or memory) with quantum computing in practical/realistic time.

We cannot scale quantum computer yet. Issue with errors and error correction.

Fault-tolerant QC have exponential and quadratic speed up shown, but need much more qubits.

Noisy intermediate scale quantum computing are up to 433 qubits.Current algorithm shown quadratic speed up. The output is approximate.

Parametrised quantum circuits - check which gates can be implemented efficiently, then use them.