Run a quantum circuit, right here
No account, no install, no queue. This runs in your browser, so the arithmetic happens on your machine and the answer is exact rather than sampled from a noisy device. Build a circuit, run it, and read the outcome probabilities directly.
Build a circuit
Two qubits that always agree: never 01, never 10. Measured this way a pair of matched coins looks identical, and the difference only shows up when you measure along a different axis. That is Bell's theorem, and it is not visible in this histogram.
h q[0];
cx q[0],q[1];Result
Exact probabilities, computed in this tab. Counts are sampled from them, so the scatter is real shot noise.
|00⟩|11⟩No error bound here, and that is the point.
Nothing above was approximated: at 2 qubits the state is 4 amplitudes and your browser holds all of them exactly. Past roughly 32 qubits no machine can, approximation becomes unavoidable, and the question stops being what the answer is and becomes how far from the truth it might be. That is what the hosted engines measure and certify.
A free online quantum circuit simulator
If you have used Quirk, the well-known browser quantum simulator by Craig Gidney, this will feel familiar: drag gates onto wires, watch the state update, no sign-up. Quirk is excellent and this is not an attempt to replace it. The difference is what happens after the sandbox.
- Same circuit, bigger engines. A browser tops out around 10 qubits because the state doubles with each one. The same circuit runs here on tensor-network and stabilizer engines past 1,000 qubits, and on real hardware, without being rewritten.
- An accuracy statement. Once a circuit leaves exact simulation, every approximate result carries a measured error bound you can cite or verify.
- Real QPUs. Five quantum processors from four vendors, at provider list price, through the same API.
For learning the gates, a browser simulator is the right tool and costs nothing. For anything you intend to publish or act on, the question becomes how far the answer might be from the truth, which is what the rest of this platform exists to answer.
Where this stops working
An exact simulation stores one complex amplitude per basis state, so an n-qubit circuit costs 16 × 2n bytes. Ten qubits is 16 KiB and instant. Thirty is 16 GiB. Forty is 16 TiB, which is no longer a laptop or a browser tab. Each qubit doubles the bill, so the distance between comfortable and impossible is about four qubits.
Past that wall the answer has to be approximated, and an approximate answer without a stated error is an assertion rather than a measurement. ZKSF runs the methods that go further, and reports how far from the truth each result might be, measured on the run rather than estimated.