def test_merge_slide():
s = cirq.Simulator()
s1, s2, t, p1, p2, a = cirq.LineQubit.range(6)
measure = cirq.Moment(cirq.measure(s1, key='s1'), cirq.measure(s2,
key='s2'),
cirq.measure(t, key='t'))
# If both paths are clear, the first source square should always be empty.
c = cirq.Circuit(cirq.X(p1), cirq.X(p2), cirq.X(s1),
qm.merge_slide(s1, t, s2, p1, p2, a), measure)
results = s.run(c, repetitions=100)
assert all(r == [0] for r in results.measurements['s1'])
def do_move(self, m: move.Move) -> int:
"""Performs a move on the quantum board.
Based on the type and variant of the move requested,
this function augments the circuit, classical registers,
and post-selection criteria to perform the board.
Returns: The measurement that was performed, or 1 if
no measurement was required.
"""
if not m.move_type:
raise ValueError('No Move defined')
if m.move_type == enums.MoveType.NULL_TYPE:
raise ValueError('Move has null type')
if m.move_type == enums.MoveType.UNSPECIFIED_STANDARD:
raise ValueError('Move type is unspecified')
# Reset accumulations here because function has conditional return branches
self.accumulations_repetitions = None
# Add move to the move move_history
self.move_history.append(m)
sbit = square_to_bit(m.source)
tbit = square_to_bit(m.target)
squbit = bit_to_qubit(sbit)
tqubit = bit_to_qubit(tbit)
if (m.move_variant == enums.MoveVariant.CAPTURE
or m.move_type == enums.MoveType.PAWN_EP
or m.move_type == enums.MoveType.PAWN_CAPTURE):
# TODO: figure out if it is a deterministic capture.
for val in list(self.allowed_pieces):
self.allowed_pieces.add(val - 1)
if m.move_type == enums.MoveType.PAWN_EP:
# For en passant, first determine the square of the pawn being
# captured, which should be next to the target.
if m.target[1] == '6':
epbit = square_to_bit(m.target[0] + '5')
elif m.target[1] == '2':
epbit = square_to_bit(m.target[0] + '4')
else:
raise ValueError(f'Invalid en passant target {m.target}')
epqubit = bit_to_qubit(epbit)
# For the classical version, set the bits appropriately
if (epqubit not in self.entangled_squares
and squbit not in self.entangled_squares
and tqubit not in self.entangled_squares):
if (not nth_bit_of(epbit, self.state)
or not nth_bit_of(sbit, self.state)
or nth_bit_of(tbit, self.state)):
raise ValueError('Invalid classical e.p. move')
self.state = set_nth_bit(epbit, self.state, False)
self.state = set_nth_bit(sbit, self.state, False)
self.state = set_nth_bit(tbit, self.state, True)
return 1
# If any squares are quantum, it's a quantum move
self.add_entangled(squbit, tqubit, epqubit)
# Capture e.p. post-select on the source
if m.move_variant == enums.MoveVariant.CAPTURE:
is_there = self.post_select_on(squbit)
if not is_there:
return 0
self.add_entangled(squbit)
path_ancilla = self.new_ancilla()
captured_ancilla = self.new_ancilla()
captured_ancilla2 = self.new_ancilla()
# capture e.p. has a special circuit
self.circuit.append(
qm.capture_ep(squbit, tqubit, epqubit, self.new_ancilla(),
self.new_ancilla(), self.new_ancilla()))
return 1
# Blocked/excluded e.p. post-select on the target
if m.move_variant == enums.MoveVariant.EXCLUDED:
is_there = self.post_select_on(tqubit)
if is_there:
return 0
self.add_entangled(tqubit)
self.circuit.append(
qm.en_passant(squbit, tqubit, epqubit, self.new_ancilla(),
self.new_ancilla()))
return 1
if m.move_type == enums.MoveType.PAWN_CAPTURE:
# For pawn capture, first measure source.
is_there = self.post_select_on(squbit)
if not is_there:
return 0
if tqubit in self.entangled_squares:
old_tqubit = self.unhook(tqubit)
self.add_entangled(squbit, tqubit)
self.circuit.append(
qm.controlled_operation(cirq.ISWAP, [squbit, tqubit],
[old_tqubit], []))
else:
# Classical case
self.state = set_nth_bit(sbit, self.state, False)
self.state = set_nth_bit(tbit, self.state, True)
return 1
if m.move_type == enums.MoveType.SPLIT_SLIDE:
tbit2 = square_to_bit(m.target2)
tqubit2 = bit_to_qubit(tbit2)
# Find all the squares on both paths
path_qubits = self.path_qubits(m.source, m.target)
path_qubits2 = self.path_qubits(m.source, m.target2)
if len(path_qubits) == 0 and len(path_qubits2) == 0:
# No interposing squares, just jump.
m.move_type = enums.MoveType.SPLIT_JUMP
else:
self.add_entangled(squbit, tqubit, tqubit2)
path1 = self.create_path_ancilla(path_qubits)
path2 = self.create_path_ancilla(path_qubits2)
ancilla = self.new_ancilla()
self.circuit.append(
qm.split_slide(squbit, tqubit, tqubit2, path1, path2,
ancilla))
return 1
if m.move_type == enums.MoveType.MERGE_SLIDE:
sbit2 = square_to_bit(m.source2)
squbit2 = bit_to_qubit(sbit2)
self.add_entangled(squbit, squbit2, tqubit)
# Find all the squares on both paths
path_qubits = self.path_qubits(m.source, m.target)
path_qubits2 = self.path_qubits(m.source2, m.target)
if len(path_qubits) == 0 and len(path_qubits2) == 0:
# No interposing squares, just jump.
m.move_type = enums.MoveType.MERGE_JUMP
else:
path1 = self.create_path_ancilla(path_qubits)
path2 = self.create_path_ancilla(path_qubits2)
ancilla = self.new_ancilla()
self.circuit.append(
qm.merge_slide(squbit, tqubit, squbit2, path1, path2,
ancilla))
return 1
if (m.move_type == enums.MoveType.SLIDE
or m.move_type == enums.MoveType.PAWN_TWO_STEP):
path_qubits = self.path_qubits(m.source, m.target)
if len(path_qubits) == 0:
# No path, change to jump
m.move_type = enums.MoveType.JUMP
if (m.move_type == enums.MoveType.SLIDE
or m.move_type == enums.MoveType.PAWN_TWO_STEP):
for p in path_qubits:
if (p not in self.entangled_squares
and nth_bit_of(qubit_to_bit(p), self.state)):
# Classical piece in the way
return 0
# For excluded case, measure target
if m.move_variant == enums.MoveVariant.EXCLUDED:
is_there = self.post_select_on(tqubit)
if is_there:
return 0
self.add_entangled(squbit, tqubit)
if m.move_variant == enums.MoveVariant.CAPTURE:
capture_ancilla = self.new_ancilla()
self.circuit.append(
qm.controlled_operation(cirq.X, [capture_ancilla],
[squbit], path_qubits))
# We need to add the captured_ancilla to entangled squares
# So that we measure it
self.entangled_squares.add(capture_ancilla)
capture_allowed = self.post_select_on(capture_ancilla)
if not capture_allowed:
return 0
else:
# Perform the captured slide
self.add_entangled(squbit)
# Remove the target from the board into an ancilla
# and set bit to zero
self.unhook(tqubit)
self.state = set_nth_bit(tbit, self.state, False)
# Re-add target since we need to swap into the square
self.add_entangled(tqubit)
# Perform the actual move
self.circuit.append(qm.normal_move(squbit, tqubit))
# Set source to empty
self.unhook(squbit)
self.state = set_nth_bit(sbit, self.state, False)
# Now set the whole path to empty
for p in path_qubits:
self.state = set_nth_bit(qubit_to_bit(p), self.state,
False)
self.unhook(p)
return 1
# Basic slide (or successful excluded slide)
# Add all involved squares into entanglement
self.add_entangled(squbit, tqubit, *path_qubits)
if len(path_qubits) == 1:
# For path of one, no ancilla needed
self.circuit.append(qm.slide_move(squbit, tqubit, path_qubits))
return 1
# Longer paths require a path ancilla
ancilla = self.new_ancilla()
self.circuit.append(
qm.slide_move(squbit, tqubit, path_qubits, ancilla))
return 1
if (m.move_type == enums.MoveType.JUMP
or m.move_type == enums.MoveType.PAWN_STEP):
if (squbit not in self.entangled_squares
and tqubit not in self.entangled_squares):
# Classical version
self.state = set_nth_bit(sbit, self.state, False)
self.state = set_nth_bit(tbit, self.state, True)
return 1
# Measure source for capture
if m.move_variant == enums.MoveVariant.CAPTURE:
is_there = self.post_select_on(squbit)
if not is_there:
return 0
self.unhook(tqubit)
# Measure target for excluded
if m.move_variant == enums.MoveVariant.EXCLUDED:
is_there = self.post_select_on(tqubit)
if is_there:
return 0
# Only convert source qubit to ancilla if target
# is empty
unhook = tqubit not in self.entangled_squares
self.add_entangled(squbit, tqubit)
# Execute jump
self.circuit.append(qm.normal_move(squbit, tqubit))
if unhook or m.move_variant != enums.MoveVariant.BASIC:
# The source is empty.
# Change source qubit to be an ancilla
# and set classical bit to zero
self.state = set_nth_bit(sbit, self.state, False)
self.unhook(squbit)
return 1
if m.move_type == enums.MoveType.SPLIT_JUMP:
tbit2 = square_to_bit(m.target2)
tqubit2 = bit_to_qubit(tbit2)
self.add_entangled(squbit, tqubit, tqubit2)
self.circuit.append(qm.split_move(squbit, tqubit, tqubit2))
self.state = set_nth_bit(sbit, self.state, False)
self.unhook(squbit)
return 1
if m.move_type == enums.MoveType.MERGE_JUMP:
sbit2 = square_to_bit(m.source2)
squbit2 = bit_to_qubit(sbit2)
self.add_entangled(squbit, squbit2, tqubit)
self.circuit.append(qm.merge_move(squbit, squbit2, tqubit))
# TODO: should the source qubit be 'unhooked'?
return 1
if m.move_type == enums.MoveType.KS_CASTLE:
# Figure out the rook squares
if sbit == square_to_bit('e1') and tbit == square_to_bit('g1'):
rook_sbit = square_to_bit('h1')
rook_tbit = square_to_bit('f1')
elif sbit == square_to_bit('e8') and tbit == square_to_bit('g8'):
rook_sbit = square_to_bit('h8')
rook_tbit = square_to_bit('f8')
else:
raise ValueError(f'Invalid kingside castling move')
rook_squbit = bit_to_qubit(rook_sbit)
rook_tqubit = bit_to_qubit(rook_tbit)
# Piece in non-superposition in the way, not legal
if (nth_bit_of(rook_tbit, self.state)
and rook_tqubit not in self.entangled_squares):
return 0
if (nth_bit_of(tbit, self.state)
and tqubit not in self.entangled_squares):
return 0
# Not in superposition, just castle
if (rook_tqubit not in self.entangled_squares
and tqubit not in self.entangled_squares):
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
return 1
# Both intervening squares in superposition
if (rook_tqubit in self.entangled_squares
and tqubit in self.entangled_squares):
castle_ancilla = self.create_path_ancilla(
[rook_tqubit, tqubit])
self.entangled_squares.add(castle_ancilla)
castle_allowed = self.post_select_on(castle_ancilla)
if castle_allowed:
self.unhook(rook_tqubit)
self.unhook(tqubit)
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
return 1
else:
self.post_selection[castle_ancilla] = castle_allowed
return 0
# One intervening square in superposition
if rook_tqubit in self.entangled_squares:
measure_qubit = rook_tqubit
measure_bit = rook_tbit
else:
measure_qubit = tqubit
measure_bit = tbit
is_there = self.post_select_on(measure_qubit)
if is_there:
return 0
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
return 1
if m.move_type == enums.MoveType.QS_CASTLE:
# Figure out the rook squares and the b-file square involved
if sbit == square_to_bit('e1') and tbit == square_to_bit('c1'):
rook_sbit = square_to_bit('a1')
rook_tbit = square_to_bit('d1')
b_bit = square_to_bit('b1')
elif sbit == square_to_bit('e8') and tbit == square_to_bit('c8'):
rook_sbit = square_to_bit('a8')
rook_tbit = square_to_bit('d8')
b_bit = square_to_bit('b8')
else:
raise ValueError(f'Invalid queenside castling move')
rook_squbit = bit_to_qubit(rook_sbit)
rook_tqubit = bit_to_qubit(rook_tbit)
b_qubit = bit_to_qubit(b_bit)
# Piece in non-superposition in the way, not legal
if (nth_bit_of(rook_tbit, self.state)
and rook_tqubit not in self.entangled_squares):
return 0
if (nth_bit_of(tbit, self.state)
and tqubit not in self.entangled_squares):
return 0
if (b_bit is not None and nth_bit_of(b_bit, self.state)
and b_qubit not in self.entangled_squares):
return 0
# Not in superposition, just castle
if (rook_tqubit not in self.entangled_squares
and tqubit not in self.entangled_squares
and b_qubit not in self.entangled_squares):
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
return 1
# Neither intervening squares in superposition
if (rook_tqubit not in self.entangled_squares
and tqubit not in self.entangled_squares):
if b_qubit not in self.entangled_squares:
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
else:
self.queenside_castle(squbit, rook_squbit, tqubit,
rook_tqubit, b_qubit)
return 1
# Both intervening squares in superposition
if (rook_tqubit in self.entangled_squares
and tqubit in self.entangled_squares):
castle_ancilla = self.create_path_ancilla(
[rook_tqubit, tqubit])
self.entangled_squares.add(castle_ancilla)
castle_allowed = self.post_select_on(castle_ancilla)
if castle_allowed:
self.unhook(rook_tqubit)
self.unhook(tqubit)
if b_qubit not in self.entangled_squares:
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
else:
self.queenside_castle(squbit, rook_squbit, tqubit,
rook_tqubit, b_qubit)
return 1
else:
self.post_selection[castle_ancilla] = castle_allowed
return 0
# One intervening square in superposition
if rook_tqubit in self.entangled_squares:
measure_qubit = rook_tqubit
measure_bit = rook_tbit
else:
measure_qubit = tqubit
measure_bit = tbit
is_there = self.post_select_on(measure_qubit)
if is_there:
return 0
if b_qubit not in self.entangled_squares:
self.set_castle(sbit, rook_sbit, tbit, rook_tbit)
else:
self.queenside_castle(squbit, rook_squbit, tqubit, rook_tqubit,
b_qubit)
return 1
raise ValueError(f'Move type {m.move_type} not supported')