Use Left mouse button to drag-and-drop a gate.
Some gates have parameters. To change a parameter, use Ctrl+left mouse button and drag left-right, or use Shift+left mouse button and drag left-right to snap the parameter to nice values. You can also click on a parameter to select it, and then use Ctrl+left arrow, Ctrl+right arrow keys to adjust, Shift+left arrow, Shift+right arrow keys to snap.

To delete a gate, you can (1) left-click on the gate to select it, and then hit the Delete key; or (2) drag the gate off the circuit and drop it outside; or (3) press+release over the gate with the Middle mouse button (like in Quirk).

To UNDO, hit the Back button in your web browser. The state of the circuit is encoded in the query string of the browser's URL (like in Quirk), hence circuits can be bookmarked and shared as hyperlinks in plain text.

Additional options: [Show...] [Hide]

Camera controls: Shift+Right mouse button drag to translate; Ctrl+Right mouse button drag left-right to zoom.
Frame Animated Frame

Clear Circuit Hit the Back button in your browser to Undo.

Expand Circuit Replaces certain gates with equivalent sequences of other gates so that their effects can be visualized on the state vector more easily, at the cost of making the circuit deeper. If generalized gates are used, then fewer levels need to be added in the expansion. See our paper for details. Hit the Back button in your browser to Undo.
Use generalized gates in the expansion to produce a shorter expansion.

Print Magic Prints Second Stabilizer Rényi Entropy of the output state to the console.

Export to Quirk:

View this circuit in Quirk (some gates may be omitted or not work)

Export to IBM:

Open IBM Quantum Composer
OpenQASM code that you can paste into IBM Quantum Composer to get the same circuit (note that not all gates are supported by IBM Quantum Composer):

Copy OpenQASM code (some gates may be omitted or not work)

Predefined circuits: [Show...] [Hide]

Bell state [reference]

How does the correlation between the qubits change if we add X^0.25 gates at the end of both qubits? And what if we do that again?
Now try this circuit: how does the correlation between the qubits change if we add X^0.25 gates at the end of both qubits?

GHZ state [reference]
GHZ-4 state
Variant of GHZ-4
W state [reference]
W-4 state adapted from here
partial entanglement followed by partial disentanglement (1)
partial entanglement followed by partial disentanglement (2)
variant of Werner state based on Figure A1 in Riedel Garding et al. 2021
circuit generating |H>^(⊗6) magic state with SSRE magic 2.490
circuit generating |T>^(⊗6) magic state with SSRE 3.510
alternative circuit generating |T>^(⊗6) magic state with SSRE 3.510
circuit with cascading CT gates with SSRE magic 2.848
circuit with cyclic CCZ gates with SSRE magic 3.696
circuit with cyclic CCT gates with SSRE magic 3.920
Different ways to implement Grover's algorithm. Each one shows 1 or 2 layers that initialize, then the oracle, then the diffusion operator. Challenge: show that these are all equivalent.

Grover example 1
Grover example 2
Grover example 3
Grover example 4

Puzzles:

Design a circuit that entangles, and then disentangles, two qubits.

example 1
example 2

Design a circuit that only partially entangles two qubits.

example 1
example 2
example 3

Design a circuit on 2 qubits, using as few gates as possible, that results in the 4 base states (00, 01, 10, 11) having 4 distinct probabilities.

candidate solution 1
candidate solution 2

Design a circuit that results in some of the base states having probabilities that follow a geometric sequence, for example, a base state with probability 50%, another with a probability of 25%, another with 12.5%, etc.

candidate solution

Design a circuit on 4 qubits that results in the same amplitude on all 16 base states, except for one base state whose phase is opposite to the others. This opposing phase, in effect, "tags" the base state as different from the others, and can simulate an oracle in Grover's algorithm.

First, do this for the state 1111, so its phase is opposite all the others, but all amplitudes have the same magnitude. candidate solution 1, candidate solution 2, candidate solution 3
Then modify the circuit so that state 1011 has its phase opposite all the others. candidate solution 1, candidate solution 2, candidate solution 3
Then try to do it for 0100. candidate solution 1
Then try for 0000. candidate solution 1

Design circuits to produce examples of each of the states in the set {pure, partially mixed, maximally mixed}×{product state, separable, partially entangled, maximally entangled}

List of definitions of matrices for quantum gates