Proposal for a loophole-free violation of Bell's inequalities with a set of single photons and homodyne measurements

Abstract

We demonstrate that different kinds of mesoscopic quantum states of light can be efficiently generated from a simple iterative scheme. These states exhibit strong non-classical features, and could be of great interest for many applications such as quantum error-correcting codes or fundamental testings. Based on these states, we further propose a protocol allowing a large loophole-free violation of a Clauser-Horne-Shimony-Holt (CHSH)-type Bellʼs inequality with significant losses, thus showing that the quantum properties of some of these states can exhibit a remarkable robustness to losses. S Online supplementary data available from stacks.iop.org/njp/16/053001/ mmedia Keywords: entanglement and quantum nonlocality, quantum information, quantum state engineering and measurements Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. New J. Phys. 16 (2014) 053001 J Etesse et al New J. Phys. 16 (2014) 053001 J Etesse et al New J. Phys. 16 (2014) 053001 J Etesse et al 4 New J. Phys. 16 (2014) 053001 J Etesse et al 5 New J. Phys. 16 (2014) 053001 J Etesse et al 6 New J. Phys. 16 (2014) 053001 J Etesse et al 7 New J. Phys. 16 (2014) 053001 J Etesse et al 9 2 , and k is the number of breeding operations. For New J. Phys. 16 (2014) 053001 J Etesse et al 13 New J. Phys. 16 (2014) 053001 J Etesse et al 15 If we write = + m k l and = − n k l, (m and n have always the same parity), we get the expression New J. Phys. 16 (2014) 053001 J Etesse et al

Experimental Generation of Squeezed Cat States with an Operation Allowing Iterative Growth

“…A very interesting point is that this experimental reali zation is the first stage of protocols of broader interest [10,37]: by iterating the operation described in the present paper, i.e., by feeding the protocol with the states we created instead of the single photons, it is possible to grow the size of the cat state and also to implement cat state repeater protocols. In other words, we have presented a proof of the concept for the cornerstone of cat breeding operation.…”

“…Homodyne heralding [10,27] seems to be a better candidate for a CS breeding operation, as the detection efficiency has no impact on the success probability of the whole operation. An important advantage of this kind of iterated method is that between each iteration, a quantum memory can be incorporated in order to increase the success probability of the whole process.…”

“…In the present paper we have performed what is, to our knowledge, the first experimental realization of this kind of protocol [10]. Let us briefly restate its principle: two single photon Fock states |1) are sent on a symmetrical beam splitter (called a breeding beam splitter in the following), and a homodyne measurement is performed on one of the two output arms, as shown on Fig.…”

Non-Gaussian and Gottesman–Kitaev–Preskill state preparation by photon catalysis

“…The decreased purity more greatly harms the procedures with larger N, unsurprisingly. However, we note that just as in [51], our protocol in of itself adds little imperfection to the result, which can be seen directly in figure 6 by comparing the drop in fidelity between neighboring values of N. For purities above γ=0.8, the decrease in the fidelity of our output state with the target between N=2 and N=3 step processes is nearly equivalent to the fidelity difference between N=3 and N=4 step procedures, which indicates the change in fidelity is nearly linear with the number of impure single-photon inputs. Figure 6 indicates the importance of pure single photons for our protocol; fortunately, there has been much work in the area of on-demand, highly efficient single-photon emitters using solid state devices [54][55][56].…”

Resource theory of quantum non-Gaussianity and Wigner negativity

“…Non-Gaussian operations can in turn be enabled by non-Gaussian states via gate teleportation, the Gaussian protocol at the basis of CV measurementbased quantum computation. However, it is not clear in general which non-Gaussian states can play this crucial enabling role [78,86,92,[104][105][106][107] and at which cost in terms of circuit synthesis [108]. As progresses in analogous problems for DV systems have been made possible by the development of the resource theory for magic states [52,64,70], we expect similar advances to be possible in the context of CV systems with the assistance of the framework introduced here.…”