Browsing by Author "Ozdemir, Sahin Kaya"

Now showing 1 - 3 of 3

Citation Count: 28
Deterministic local doubling of W states
(Optical Soc Amer, 2016) Yesilyurt, Can; Bugu, Sinan; Ozaydin, Fatih; Altintas, Azmi Ali; Tame, Mark; Yang, Lan; Ozdemir, Sahin Kaya
In large quantum systems, multipartite entanglement can be found in many inequivalent classes. Preparing states of arbitrary size in different classes is important for performing a wide range of quantum protocols. W states, in particular, constitute a class with a variety of quantum networking protocols. However, all known schemes for preparing polarization encoded photonic W states are probabilistic, with resource requirements increasing at least sub-exponentially. We propose a deterministic scheme for preparing W states of size of any power of 2, which requires no prior entanglement and can be performed locally. We introduce an all-optical setup that can efficiently double the size of W states of arbitrary size. Our scheme advances the use of W states in real-world quantum networks and could be extended to other physical systems. (C) 2016 Optical Society of America
Citation Count: 68
Fusing multiple W states simultaneously with a Fredkin gate
(Amer Physical Soc, 2014) Ozaydin, Fatih; Bugu, Sinan; Yesilyurt, Can; Altintas, Azmi Ali; Tame, Mark; Ozdemir, Sahin Kaya
We propose an optical scheme to prepare large-scale entangled networks of W states. The scheme works by simultaneously fusing three polarization-encoded W states of arbitrary size via accessing only one qubit of each W state. It is composed of a Fredkin gate (controlled-swap gate), two fusion gates [as proposed in S. K. Ozdemir et al., New J. Phys. 13, 103003 (2011)], and an H-polarized ancilla photon. Starting with three n-qubit W states, the scheme prepares a new W state with 3(n - 1) qubits after postselection if both fusion gates operate successfully, i.e., a fourfold coincidence at the detectors. The proposed scheme reduces the cost of creating arbitrarily large W states considerably when compared to previously reported schemes.
Citation Count: 0
Superadditivity of Quantum Channel Capacity
(Amer inst Physics, 2012) Ozaydin, Fatih; Ozdemir, Sahin Kaya; Koashi, Masato; Imoto, Nobuyuki
Superadditivity of quantum capacity of communication channels is one of the most interesting findings of the field. Yard and Smith, finding a relation between the private capacity and the assisted quantum capacity, showed a striking example of superadditivity, i.e. two channels of zero quantum capacity could achieve a positive quantum capacity when used together [1]. The four dimensional channels they used are a 50% erasure channel (therefore zero quantum capacity, due to no-cloning theorem) and a Horodecki channel (again zero quantum capacity due to incapability of sharing free entanglement). In this work we present the more general cases of superadditivity. Directly calculating the lower bounds of joint quantum capacities without using the relation between private capacity and assisted quantum capacity, we examine scenarios considering erasure channels of arbitrary probabilities and different Horodecki channels, and discuss the roles of degradability and anti-degradability as well as the role of the private capacity in superadditivity. We also derive an upper bound for the joint quantum capacity for the superactivation case.