4 Nonlocal Games: Working with multiple qubits

4.1  Nonlocal Games

At this point, we have seen how single-qubit devices can be programmed to accomplish useful tasks such as random number generation and quantum key distribution. The most exciting computational tasks, however, require using multiple qubits together. In this chapter, you will learn about nonlocal games: a way to validate our quantum mechanical descriptions of the universe with friends with multi-qubit systems.

We will dive into a new Python package called QuTiP that will allow us to program quantum systems faster and has some cool built-in features for simulating quantum mechanics. Then you will to learn how to leverage QuTiP and program a simulator for multiple qubits and see how that changes (or doesn’t!) the 3 main tasks for our qubits: state preparations, operations, and measurement.

4.1.1  What are nonlocal games?

4.1.2  Testing quantum physics itself: The CHSH game

4.1.3  Classical strategy

4.2  Working with multiple qubit states

4.2.1  Registers

4.2.2  Why is it hard to simulate quantum computers?

4.2.3  Tensor products for state preparation

4.2.4  Tensor products for qubit operations on registers

4.3  QuTiP of the Iceberg

4.3.1  Quantum objects in QuTiP

4.3.2  Upgrading the simulator

4.3.3  Measuring up: How can we measure multiple qubits?

4.4  CHSH: Quantum strategy

4.5  Summary