% Simple examples for Quack!
% by Peter Rohde

quack

% Prepare a Bell state and look at the reduced density matrix for one of the qubits
disp('*** Example 1 ***')
disp(' ')

init_state(2)
prepare_bell_00(1,2)

disp('Density matrix of an EPR pair:')
print_dm
disp(' ')
disp('Reduced density matrix for the first qubit (should be a completely mixed state):')
print_rdm(1)
disp(' ')

input('Press <<return>> to go to the next example');
disp(' ')

% Prepare a Bell state using a product state and a CNOT gate
disp('*** Example 2 ***')
disp(' ')

disp('Prepare the state |+>|0>:')
init_state(2)
prepare_plus(1)
print_dm;

disp(' ')
disp('Apply a CNOT gate (we should get an EPR pair):')

cnot(1,2)
print_dm

disp(' ')
disp('Reduced density matrix of first qubit:')
print_rdm(1)

input('Press <<return>> to go to the next example');
disp(' ')

% Bit-flip channel
disp('*** Example 3 ***')
disp(' ')

disp('Prepare the |0> state and apply a p=0.5 bit-flip channel (should get a completely mixed state):')

init_state(1)
X_ch(0.5,1)
print_hist
print_dm

disp('Now prepare the |+> state and apply a p=0.5 bit-flip channel (state shouldn''t change):')

init_state(1)
prepare_plus(1)
X_ch(0.5,1)
print_hist
print_dm

input('Press <<return>> to go to the next example');
disp(' ')

% Circuit history
disp('*** Example 4 ***')
disp(' ')
disp('Construct a circuit containing state preparation, simple gates and measurment, and show the circuit history:')

init_state(5)
prepare_one(1)
prepare_plus(2)
prepare_minus(3)
prepare_bell_00(4,5)

cnot(1,2)
Y(3)
H(4)
Rz(pi,5)
swap(1,5)
cz(2,3)
Z_measure(1);
Z_measure(2);
bell_measure(3,4);
T(5)
Z_measure(5);

print_hist