A 5-qubit quantum computer

Let’s take this even further and look at a 5-qubit quantum computer.

Using Hadamard and CNOT gates we can create a state where we either measure all zeros or all ones. This is a maximally entangled state. And it even has a special name: GHZ state (named after three guys: Greenberger, Horne, and Zeilinger). It can be used to assess how well entanglement works on a real quantum device. See below for a real 5-qubit device that IQM Quantum Computers built.

My measurements

After 1000 measurements we get the following distribution:

How many gates do we need at least to create this state?

• A

  3

• B

  4

• C

  5

• D

  6

Well done! There are multiple ways to do this. Here is an image of (perhaps another) solution:

Not quite. Give this circuit a try:

Did you know? Finland's first quantum computer has 5 qubits and was delivered by IQM.