Starter circuits

Each starter circuit is generated on the fly for the number of qubits you choose, and every card shows its live Penrose diagram. Open in applet loads it for interactive contraction, where you can also change the remaining parameters (number of Pauli terms, Trotter steps, couplings, seed and so on). Static copies of the circuits are also in the examples/ folder as .qasm files.

Things to try

• GHZ: contract greedily and watch the intermediate rank stay small (a chain of COPY tensors is an MPS with bond dimension 2). Then switch to the time sweep and see the cost grow to the full 2ⁿ state vector.
• 10 Pauli terms: in expectation mode (e.g. P = Z0 Z1), compare the greedy cost with the qubit-by-qubit sweep. The doubled network U P U† is twice as large, yet the greedy order often stays cheap.
• Ising: increase the Trotter steps and observe how the greedy peak rank grows with circuit depth, the signature of growing entanglement.
• QFT: the all-to-all controlled-phase ladder is dense. Try clicking your own order and try to beat the greedy cost.