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MPS: Unite the common part of apply_2_qubit_gate and apply_swap_internal (#906)

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merav-aharoni 2020-09-10 22:14:34 +03:00 committed by GitHub
parent 42e9ca9a72
commit 88fddc313d
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2 changed files with 21 additions and 32 deletions
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50
src/simulators/matrix_product_state/matrix_product_state_internal.cpp
View File

@ -380,43 +380,20 @@ void MPS::apply_swap_internal(uint_t index_A, uint_t index_B, bool swap_gate) {
}
return;
}
// when actual_A+1 == actual_B then we can really do the swap
MPS_Tensor A = q_reg_[actual_A], B = q_reg_[actual_B];
//There is no lambda on the edges of the MPS
if (actual_A != 0)
q_reg_[actual_A].mul_Gamma_by_left_Lambda(lambda_reg_[actual_A-1]);
if (actual_B != num_qubits_-1)
q_reg_[actual_B].mul_Gamma_by_right_Lambda(lambda_reg_[actual_B]);
MPS_Tensor temp = MPS_Tensor::contract(q_reg_[actual_A], lambda_reg_[actual_A], q_reg_[actual_B]);
temp.apply_swap();
MPS_Tensor left_gamma,right_gamma;
rvector_t lambda;
MPS_Tensor::Decompose(temp, left_gamma, lambda, right_gamma);
//There is no lambda on the edges of the MPS
if (actual_A != 0)
left_gamma.div_Gamma_by_left_Lambda(lambda_reg_[actual_A-1]);
if (actual_B != num_qubits_-1)
right_gamma.div_Gamma_by_right_Lambda(lambda_reg_[actual_B]);
q_reg_[actual_A] = left_gamma;
lambda_reg_[actual_A] = lambda;
q_reg_[actual_B] = right_gamma;
// when actual_A+1 == actual_B then we can really do the swap between A and A+1
common_apply_2_qubit_gate(actual_A, Gates::swap,
cmatrix_t(1, 1) /*dummy matrix*/, false /*swapped*/);
if (!swap_gate) {
// we are moving the qubit at index_A one position to the right
// and the qubit at index_B or index_A+1 is moved one position
// we move the qubit at index_A one position to the right
// and the qubit at index_B (or index_A+1) is moved one position
//to the left
std::swap(qubit_ordering_.order_[index_A], qubit_ordering_.order_[index_B]);
}
// update qubit location after all the swaps
if (!swap_gate)
// update qubit locations after all the swaps
for (uint_t i=0; i<num_qubits_; i++)
qubit_ordering_.location_[qubit_ordering_.order_[i]] = i;
}
}
//-------------------------------------------------------------------------
@ -450,6 +427,12 @@ void MPS::apply_2_qubit_gate(uint_t index_A, uint_t index_B, Gates gate_type, co
A = index_A - 1;
swapped = true;
}
common_apply_2_qubit_gate(A, gate_type, mat, swapped);
}
void MPS::common_apply_2_qubit_gate(uint_t A, // the gate is applied to A and A+1
Gates gate_type, const cmatrix_t &mat,
bool swapped) {
// After we moved the qubits as necessary,
// the operation is always between qubits A and A+1
@ -468,6 +451,9 @@ void MPS::apply_2_qubit_gate(uint_t index_A, uint_t index_B, Gates gate_type, co
case cz:
temp.apply_cz();
break;
case swap:
temp.apply_swap();
break;
case id:
break;
case cu1:
@ -772,7 +758,7 @@ void MPS::move_qubits_to_right_end(const reg_t &qubits,
void MPS::change_position(uint_t src, uint_t dst) {
if(src == dst)
return;
else if(src < dst)
if(src < dst)
for(uint_t i = src; i < dst; i++) {
apply_swap_internal(i, i+1, false);
}

3
src/simulators/matrix_product_state/matrix_product_state_internal.hpp
View File

@ -281,6 +281,9 @@ private:
void apply_swap_internal(uint_t index_A, uint_t index_B, bool swap_gate=false);
void apply_2_qubit_gate(uint_t index_A, uint_t index_B,
Gates gate_type, const cmatrix_t &mat);
void common_apply_2_qubit_gate(uint_t index_A,
Gates gate_type, const cmatrix_t &mat,
bool swapped);
void apply_3_qubit_gate(const reg_t &qubits, Gates gate_type, const cmatrix_t &mat);
void apply_matrix_internal(const reg_t & qubits, const cmatrix_t &mat);
// apply_matrix for more than 2 qubits