Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimal linear optical discrimination of Bell-like states   Quantum information processing using linear optics is challenging due to the
limited set of deterministic operations achievable without using complicated
resource-intensive methods. While techniques such as the use of ancillary
photons can enhance the information processing capabilities of linear optical
systems they are technologically demanding. Therefore, determining the
constraints posed by linear optics and optimizing linear optical operations for
specific tasks under those constraints, without the use of ancillas, can
facilitate their potential implementation. Here, we consider the task of
unambiguously discriminating between Bell-like states without the use of
ancillary photons. This is a basic problem relevant in diverse settings, for
example, in the measurement of the output of an entangling quantum circuit or
for entanglement swapping at a quantum repeater station. While it is known that
exact Bell states of two qubits can be discriminated with an optimal success
probability of 50% we find, surprisingly, that for Bell-like states the optimal
probability can be only 25%. We analyze a set of Bell-like states in terms of
their distinguishability, entanglement as measured by concurrence, and
parameters of the beam-splitter network used for unambiguous discrimination.
Further, we provide the linear optical configuration comprised of single photon
detectors and beam splitters with input state-dependent parameters that
achieves optimal discrimination in the Bell-like case.

11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom