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# Tag Info

### Finding the norm of a Hamiltonian

The spectral norm $\|H\|$ (sometimes denoted$^1$ $\|H\|_2$ or $\|H\|_\infty$) in this case is the largest eigenvalue of $H$. There's no meaningful bound for this number without having additional ...
• 4,537
Accepted

### How to perform a controlled Pauli string rotation gate?

This is nearly a built-in decomposition in cirq. Here's what happens when you decompose a Pauli product: ...
• 21.8k
Accepted

### What does PhISwap gate mean in Cirq?

In Cirq, the PhasedISwapPowGate (i.e. PhISwap) is a fractional ISWAP conjugated by Z rotations. With phase exponent $p$ and ...
• 1,626
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### noisy circuit by openfermion

Note that OpenFermion interoperates with cirq to provide many features that are not specific to quantum chemistry. You can add noise to your circuits like this ...
• 13k
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### implement variational quantum eigensolver with openfermion

I recommend using OpenFermion in conjunction with QCOR, a quantum programming language being developed at Oak Ridge National Laboratory. This tool offers python bindings and has abstractions for ...
• 440
Accepted

### Hartree Fock state in Openfermion

The Hartree-Fock state in Openfermion has $1$'s in the left positions, and $0$'s in the right positions. In other words, the spin orbitals (i.e: the qubits) are ordered from least energy to most ...
• 381
1 vote
Accepted

### Evaluating $\texttt{FermionOperator}$ equality in Openfermion

This looks like a bug$^1$. Look at following lines of code from the v1.3.0 release branch for the implementation of SymbolicOperator.isclose (which implements ...
• 4,537
1 vote
Accepted

### Compute expectation value of an operator in openfermion

From the openfermion documentation (see here), it says the operator must be a scipy.sparse matrix. So, replacing ...
• 381
1 vote

### Openfermion : get_sparse_operator issue

This is normal! If you look at the molecular Hamiltonian ozone_molecule.get_molecular_hamiltonian(), you will notice that it is a Hamiltonian that acts on 30 spin ...
• 381
1 vote

### How to get a molecular Hamiltonians in OpenFermion

Qiskit allows you to build the customized geometry of the molecule. You can also adjust the charge and multiplicity. For example, to build the Hydrogen molecule with a given equilibrium distance ED, ...
• 37

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