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tankya2
2023-08-17 13:23:29 +08:00
parent 3fafe2b3ff
commit 89bdbfbe68
3 changed files with 89 additions and 77 deletions
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69
src/qibotn/MPSUtils.py
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@@ -2,73 +2,80 @@ import cupy as cp
from cuquantum.cutensornet.experimental import contract_decompose
from cuquantum import contract
def initial(num_qubits, dtype):
"""
Generate the MPS with an initial state of |00...00>
Generate the MPS with an initial state of |00...00>
"""
state_tensor = cp.asarray([1, 0], dtype=dtype).reshape(1,2,1)
state_tensor = cp.asarray([1, 0], dtype=dtype).reshape(1, 2, 1)
mps_tensors = [state_tensor] * num_qubits
return mps_tensors
def mps_site_right_swap(
mps_tensors,
i,
**kwargs
):
def mps_site_right_swap(mps_tensors, i, **kwargs):
"""
Perform the swap operation between the ith and i+1th MPS tensors.
"""
# contraction followed by QR decomposition
a, _, b = contract_decompose('ipj,jqk->iqj,jpk', *mps_tensors[i:i+2], algorithm=kwargs.get('algorithm',None), options=kwargs.get('options',None))
mps_tensors[i:i+2] = (a, b)
a, _, b = contract_decompose(
"ipj,jqk->iqj,jpk",
*mps_tensors[i : i + 2],
algorithm=kwargs.get("algorithm", None),
options=kwargs.get("options", None)
)
mps_tensors[i : i + 2] = (a, b)
return mps_tensors
def apply_gate(
mps_tensors,
gate,
qubits,
**kwargs
):
def apply_gate(mps_tensors, gate, qubits, **kwargs):
"""
Apply the gate operand to the MPS tensors in-place.
Args:
mps_tensors: A list of rank-3 ndarray-like tensor objects.
The indices of the ith tensor are expected to be the bonding index to the i-1 tensor,
mps_tensors: A list of rank-3 ndarray-like tensor objects.
The indices of the ith tensor are expected to be the bonding index to the i-1 tensor,
the physical mode, and then the bonding index to the i+1th tensor.
gate: A ndarray-like tensor object representing the gate operand.
The modes of the gate is expected to be output qubits followed by input qubits, e.g,
``A, B, a, b`` where ``a, b`` denotes the inputs and ``A, B`` denotes the outputs.
gate: A ndarray-like tensor object representing the gate operand.
The modes of the gate is expected to be output qubits followed by input qubits, e.g,
``A, B, a, b`` where ``a, b`` denotes the inputs and ``A, B`` denotes the outputs.
qubits: A sequence of integers denoting the qubits that the gate is applied onto.
algorithm: The contract and decompose algorithm to use for gate application.
algorithm: The contract and decompose algorithm to use for gate application.
Can be either a `dict` or a `ContractDecomposeAlgorithm`.
options: Specify the contract and decompose options.
options: Specify the contract and decompose options.
Returns:
The updated MPS tensors.
"""
n_qubits = len(qubits)
if n_qubits == 1:
# single-qubit gate
i = qubits[0]
mps_tensors[i] = contract('ipj,qp->iqj', mps_tensors[i], gate, options=kwargs.get('options',None)) # in-place update
mps_tensors[i] = contract(
"ipj,qp->iqj", mps_tensors[i], gate, options=kwargs.get("options", None)
) # in-place update
elif n_qubits == 2:
# two-qubit gate
i, j = qubits
if i > j:
# swap qubits order
return apply_gate(mps_tensors, gate.transpose(1,0,3,2), (j, i), **kwargs)
elif i+1 == j:
return apply_gate(mps_tensors, gate.transpose(1, 0, 3, 2), (j, i), **kwargs)
elif i + 1 == j:
# two adjacent qubits
a, _, b = contract_decompose('ipj,jqk,rspq->irj,jsk', *mps_tensors[i:i+2], gate, algorithm=kwargs.get('algorithm',None), options=kwargs.get('options',None))
mps_tensors[i:i+2] = (a, b) # in-place update
a, _, b = contract_decompose(
"ipj,jqk,rspq->irj,jsk",
*mps_tensors[i : i + 2],
gate,
algorithm=kwargs.get("algorithm", None),
options=kwargs.get("options", None)
)
mps_tensors[i : i + 2] = (a, b) # in-place update
else:
# non-adjacent two-qubit gate
# step 1: swap i with i+1
mps_site_right_swap(mps_tensors, i, **kwargs)
# step 2: apply gate to (i+1, j) pair. This amounts to a recursive swap until the two qubits are adjacent
apply_gate(mps_tensors, gate, (i+1, j), **kwargs)
apply_gate(mps_tensors, gate, (i + 1, j), **kwargs)
# step 3: swap back i and i+1
mps_site_right_swap(mps_tensors, i, **kwargs)
else: