Quantum Technology Initiative Journal Club

Thursday 26 Mar 2026, 16:00 → 17:00 Europe/Zurich

513/R-070 - Openlab Space (CERN)

Michele Grossi (CERN)

Weekly Journal Club meetings organised in the framework of the CERN Quantum Technology Initiative (QTI) to present and discuss scientific papers in the field of quantum science and technology. The goal is to help researchers keep track of current findings and walk away with ideas for their own research. Some previous knowledge of quantum physics would be helpful, but is not required to follow the talks.

To propose a paper for discussion, contact: michele.grossi@cern.ch

16:00 → 17:00 CERN QTI Journal CLUB

Convener: Dr Michele Grossi (CERN)

16:00 Francesco Paganelli (CERN) - Overview of Fermion-to-Qubit mappings

Abstract:
An essential step in encoding fermionic Hamiltonians on quantum computers is constructing Pauli operator representations that capture fermionic statistics. Multiple encoding schemes exist, and their choice strongly impacts the quantum resources required for representing and simulating the Hamiltonian. In this review, we examine two classes of fermion-to-qubit mappings: non-local and local encodings.

Non-local mappings, including the Jordan–Wigner, Bravyi–Kitaev, and parity transformations, encode fermionic anti-commutation relations directly into Pauli operators, resulting in operator strings whose length generally grows with system size. In contrast, local encodings shift this non-locality into highly entangled subspaces of an enlarged Hilbert space, yielding operators with local support at the cost of additional qubit overhead.

We further distinguish two subclasses of local encodings. The first, exemplified by the Verstraete–Cirac construction, introduces auxiliary Majorana degrees of freedom and leverages the Jordan-Wigner transformation to cancel long strings of Pauli operators. The second class, including approaches such as the Bravyi–Kitaev superfast mapping, assigns qubits depending on the interaction graph and encodes fermionic operators through products of local edge and vertex operators.

We compare these approaches in terms of operator locality, qubit overhead, and suitability for quantum simulation.

Speaker: Francesco Paganelli (Leiden University (NL))