quantum2/
gate.rs

1//! Gate library code (public for pedagogical reasons).
2
3use ket::Ket;
4use matrix::Matrix;
5
6/// Represents a _quantum gate_: a quantum regster transformation.
7///
8/// This gate is tagged with a `width`, and contains a unitary matrix
9/// representing the numerical transformation in the computational
10/// basis.
11///
12/// This gate may be _applied_ to a ket to update the ket's state.
13///
14/// Currently we do not check whether the matrix is unitary.
15///
16/// See [Wikipedia](https://en.wikipedia.org/wiki/Quantum_computing#Operation)
17/// for more information.
18#[derive(Debug, PartialEq)]
19pub struct Gate {
20    width: usize,
21    matrix: Matrix,
22}
23
24impl Gate {
25    /// Construct a new quantum gate, given `width` and computational basis matrix.
26    ///
27    /// Currently we do not check whether the matrix is unitary.
28    ///
29    /// # Panics
30    ///
31    /// We panic if the supplied matrix is non-square or not of dimension `width`.
32    pub fn new(width: usize, matrix: Matrix) -> Gate {
33        assert_eq!(Ket::size(width), matrix.size());
34
35        // TODO check that det(matrix) == 1
36
37        Gate {
38            width: width,
39            matrix: matrix,
40        }
41    }
42
43    /// Width of the gate.
44    pub fn width(&self) -> usize {
45        self.width
46    }
47
48    /// Representative matrix.
49    pub fn matrix(&self) -> &Matrix {
50        &self.matrix
51    }
52
53    /// Permute the qubits on which we act.
54    ///
55    /// Qubit _i_ will be acted on as qubit _permutation[i]_ was before.
56    ///
57    /// TODO: The consumer has to work out the (complicated) matrix permutation.  We ought to
58    ///       be able to compute this ourselves from a qubit permutation.
59    ///
60    /// # Panics
61    ///
62    /// We panic if set(permutation) != {0, ..., self.size - 1}.
63    pub fn permute(&self, permutation: Vec<usize>) -> Gate {
64        let m = self.matrix.permute_rows(permutation);
65
66        Gate::new(self.width, m)
67    }
68}
quantum2/gate.rs

quantum2/
gate.rs
