Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Arbitrarily many independent observers can share the nonlocality of a
  single maximally entangled qubit pair   Alice and Bob each have half of a pair of entangled qubits. Bob measures his
half and then passes his qubit to a second Bob who measures again and so on.
The goal is to maximize the number of Bobs that can have an expected violation
of the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality with the single Alice.
This scenario was introduced in [Phys. Rev. Lett. 114, 250401 (2015)] where the
authors mentioned evidence that when the Bobs act independently and with
unbiased inputs then at most two of them can expect to violate the CHSH
inequality with Alice. Here we show that, contrary to this evidence,
arbitrarily many independent Bobs can have an expected CHSH violation with the
single Alice. Our proof is constructive and our measurement strategies can be
generalized to work with a larger class of two-qubit states that includes all
pure entangled two-qubit states. Since violation of a Bell inequality is
necessary for device-independent tasks, our work represents a step towards an
eventual understanding of the limitations on how much device-independent
randomness can be robustly generated from a single pair of qubits.

30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph