I Calculating qubit purity/entanglement in a quantum computer

  • Thread starter Thread starter Bob Walance
  • Start date Start date
  • Tags Tags
    Entanglement Qubit
Click For Summary
The discussion focuses on calculating the "purity of reduced states" in a quantum computer simulator, a metric previously referred to as "entanglement." The author successfully developed a method to compute these values, which align with those provided by IBM's simulator for various quantum circuits. The document detailing this calculation method is shared for others to utilize. The purity values are consistent across different gate operations, including one-qubit gates and CNOT gates. This information may benefit others working with quantum computing simulations.
Bob Walance
Insights Author
Gold Member
Messages
82
Reaction score
55
I had written a simulator for a quantum computer and wanted to be able to calculate the values of the "purity of reduced states".

"Purity of reduced states" is a quantity that IBM provides on their simulator for each qubit. They used to call it "entanglement", and I believe that the two terms are synonymous since all of the qubits in a quantum computer start out in a pure state.

After struggling to find examples for how to calculate these purity/entanglement values for each qubit, I did finally figure it out. Attached is a document describing how to do this. The values calculated with this method jibe with IBM's simulator for various quantum circuits including simple one-qubit gates, CNOT gates, Toffoli gates, and various combinations of those.

Perhaps someone will find this useful.
 

Attachments

Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
416
  • · Replies 22 ·
Replies
22
Views
4K
  • · Replies 10 ·
Replies
10
Views
529
Replies
42
Views
4K
Replies
8
Views
5K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K