We investigate the ground state of a (1+1)-dimensional conformal field theory built with $M$ species of massless free Dirac fermions coupled at one boundary point via a conformal junction/interface. Each CFT represents a wire of finite length $L$. We develop a systematic strategy to compute the Rényi entropies for a generic bipartition between the wires and the entanglement negativity between two non-complementary sets of wires. Both these entanglement measures turn out to grow logarithmically with $L$ with an exactly calculated universal prefactor depending on the details of the junction and of the bipartition. These analytic predictions are tested numerically for junctions of free Fermi gases, finding perfect agreement.
The negativity core of a 1+1D massless scalar quantum field
Nordita, Stockholm University and KTH Royal Institute of Technology（诺迪塔，斯德哥尔摩大学和皇家理工学院）；Department of Computational and Data Sciences, Indian Institute of Science（印度科学学院计算与数据科学系）；Malmö University（马尔默大学）
Exact calculation of entanglement negativity for a 1+1D massless scalar field using phase space methods
Nordita, Stockholm University and KTH Royal Institute of Technology（诺迪塔，斯德哥尔摩大学和皇家理工学院）；Department of Physical Sciences, Indian Institute of Science Education and Research (IISER) Mohali（印度科学教育与研究所（IISER）莫哈利物理科学系）；Department of Computational and Data Sciences, Indian Institute of Science, Bangalore（印度科学学院班加罗尔计算与数据科学系）；Department of Materials Science and Applied Mathematics, Malmö University（马尔默大学材料科学与应用数学系）
