From 56a3aa7c39330e629f6485b4cf1bd3ea2fa0bf0d Mon Sep 17 00:00:00 2001
From: Wong Zi Cheng <70616433+chmwzc@users.noreply.github.com>
Date: Tue, 7 Nov 2023 07:09:05 +0000
Subject: [PATCH] Clean up earlier expectation from samples code

Also fixes documentation line in `pyproject.toml`
---
 pyproject.toml                           |  2 +-
 src/qibochem/measurement/basis_rotate.py | 27 ----------
 src/qibochem/measurement/expectation.py  | 69 +-----------------------
 3 files changed, 2 insertions(+), 96 deletions(-)
 delete mode 100644 src/qibochem/measurement/basis_rotate.py

diff --git a/pyproject.toml b/pyproject.toml
index 7b40d51..16ccd25 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ authors = ["The Qibo team"]
 license = "Apache License 2.0"
 readme = "README.md"
 repository = "https://github.com/qiboteam/qibochem/"
-documentation = ""
+documentation = "https://qibo.science/qibochem/latest/"
 keywords = []
 classifiers = [
   "Programming Language :: Python :: 3",
diff --git a/src/qibochem/measurement/basis_rotate.py b/src/qibochem/measurement/basis_rotate.py
deleted file mode 100644
index 69ba37f..0000000
--- a/src/qibochem/measurement/basis_rotate.py
+++ /dev/null
@@ -1,27 +0,0 @@
-import qibo
-from qibo import gates
-from qibo.models import Circuit
-
-
-def measure_rotate_basis(pauli_op, nqubits):
-    """
-    rotate each qubit to computational basis (Z-basis) for measurement
-    input:
-        pauli_op: qubit operator
-        nqubits: number of qubits
-    output:
-        qibo circuit with rotations and measurement gates
-    """
-
-    mqc = Circuit(nqubits)
-    for p in pauli_op:
-        if p[1] == "Z":
-            mqc.add(gates.M(p[0]))
-        elif p[1] == "Y":
-            mqc.add(gates.S(p[0]).dagger())
-            mqc.add(gates.H(p[0]))
-            mqc.add(gates.M(p[0]))
-        elif p[1] == "X":
-            mqc.add(gates.H(p[0]))
-            mqc.add(gates.M(p[0]))
-    return mqc
diff --git a/src/qibochem/measurement/expectation.py b/src/qibochem/measurement/expectation.py
index 48e7d88..385a063 100644
--- a/src/qibochem/measurement/expectation.py
+++ b/src/qibochem/measurement/expectation.py
@@ -3,73 +3,6 @@
 from qibo.hamiltonians import SymbolicHamiltonian
 from qibo.symbols import Z
 
-from qibochem.measurement.basis_rotate import measure_rotate_basis
-
-
-def pauli_expectation_shots(qc, nshots):
-    """
-    Calculates expectation value of circuit for pauli string from shots
-
-    Args:
-        qc: quantum circuit with appropriate rotations and measure gates
-        nshots: number of shots
-
-    Returns:
-        expectation: expectation value
-    """
-    result = qc.execute(nshots=nshots)
-    meas = result.frequencies(binary=True)
-
-    bitcount = 0
-    for bitstring, count in meas.items():
-        if bitstring.count("1") % 2 == 0:
-            bitcount += count
-        else:
-            bitcount -= count
-    expectation = bitcount / nshots
-    return expectation
-
-
-def circuit_expectation_shots(qc, of_qubham, nshots=1000):
-    """
-    Calculates expectation value of qubit hamiltonian w.r.t. circuit ansatz using shots
-
-    Args:
-        qc: Quantum circuit with ansatz
-        of_qubham: Molecular Hamiltonian given as an OpenFermion QubitOperator
-
-    Returns:
-        Expectation value of of_qubham w.r.t. circuit ansatz
-    """
-    # nterms = len(of_qubham.terms)
-    nqubits = qc.nqubits
-    # print(nterms)
-    coeffs = []
-    strings = []
-
-    expectation = 0
-    for qubop in of_qubham.terms:
-        coeffs.append(of_qubham.terms[qubop])
-        strings.append([qubop])
-
-    istring = 0
-    for pauli_op in strings:
-        if len(pauli_op[0]) == 0:  # no pauli obs to measure,
-            expectation += coeffs[istring]
-            # print(coeffs[istring])
-        else:
-            # add rotation gates to rotate pauli observable to computational basis
-            # i.e. X to Z, Y to Z
-            meas_qc = measure_rotate_basis(pauli_op[0], nqubits)
-            full_qc = qc + meas_qc
-            # print(full_qc.draw())
-            pauli_op_exp = pauli_expectation_shots(full_qc, nshots)
-            expectation += coeffs[istring] * pauli_op_exp
-            ## print(pauli_op, pauli_op_exp, coeffs[istring])
-        istring += 1
-
-    return expectation
-
 
 def expectation(
     circuit: qibo.models.Circuit, hamiltonian: SymbolicHamiltonian, from_samples=False, n_shots=1000
@@ -82,7 +15,7 @@ def expectation(
         circuit (qibo.models.Circuit): Quantum circuit ansatz
         hamiltonian (SymbolicHamiltonian): Molecular Hamiltonian
         from_samples: Whether the expectation value calculation uses samples or the simulated
-            state vector. Default: False, state vector simulation
+            state vector. Default: False; Results are from a state vector simulation
         n_shots: Number of times the circuit is run for the from_samples=True case
 
     Returns: