Realizing a Deterministic Source of Multipartite-Entangled Photonic Qubits

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting. While multi-mode entangled states of radiation have been generated in various platforms, all previous experiments are either probabilistic or restricted to generate specific types of states with a moderate entanglement length. Here, we demonstrate the fully deterministic generation of purely photonic entangled states such as the cluster, GHZ, and W state by sequentially emitting microwave photons from a controlled auxiliary system into a waveguide. We tomographically reconstruct the entire quantum many-body state for up to $N=4$ photonic modes and infer the quantum state for even larger $N$ from process tomography. We estimate that localizable entanglement persists over a distance of approximately ten photonic qubits, outperforming any previous deterministic scheme

Exchange hazards, relational reliability, and contracts in China: The contingent role of legal enforceability

Building on institutional and transaction cost economics, this article proposes that legal enforceability increases the use of contract over relational reliability (e.g., beliefs that the other party acts in a non-opportunistic manner) to safeguard market exchanges characterized by non-trivial hazards. The results of 399 buyer-supplier exchanges in China show that: (1) when managers perceive that the legal system can protect their firm's interests, they tend to use explicit contracts rather than relational reliability to safeguard transactions involving risks (i.e., asset specificity, environmental uncertainty, and behavioral uncertainty); and (2) when managers do not perceive the legal system as credible, they are less likely to use contracts, and instead rely on relational reliability to safeguard transactions associated with specialized assets and environmental uncertainty, but not those involving behavioral uncertainty. We further find that legal enforceability does not moderate the effect of relational reliability on contracts, but does weaken the effect of contracts on relational reliability. These results endorse the importance of prior experience (e.g., relational reliability) in supporting the use of explicit contracts, and alternatively suggest that, under conditions of greater legal enforceability, the contract signals less regarding one's intention to be trustworthy but more about the efficacy of sanctions. © 2010 Academy of International Business All rights reserved.postprin

Angel investor's selection criteria: a comparative institutional perspective

Despite the important role of angel investors as critical financial providers for new ventures, little is known regarding how institutions make their investment decisions. While angels make decisions based on selection criteria during the first stage, they are also embedded within and affected by different institutional settings and as a result weight these criteria differently than other investors. We compare angel investors' selection criteria in China and Denmark using the comparative institutional perspective. We use a policy capturing approach and hierarchy linear modeling, revealing that since Chinese angels are embedded within relationship-based institutional settings they tend to reply more on strong ties such as family and friends in management team, as well as weighting risks less compared to Danish angels operating within more rule-based institutional contexts

Realizing a deterministic source of multipartite-entangled photonic qubits

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting. Generation of multi-mode entangled states of radiation with a large entanglement length, that is neither probabilistic nor restricted to generate specific types of states, remains challenging. Here, we demonstrate the fully deterministic generation of purely photonic entangled states such as the cluster, GHZ, and W state by sequentially emitting microwave photons from a controlled auxiliary system into a waveguide. We tomographically reconstruct the entire quantum many-body state for up to N = 4 photonic modes and infer the quantum state for even larger N from process tomography. We estimate that localizable entanglement persists over a distance of approximately ten photonic qubits.ISSN:2041-172

Realization of a Universal Quantum Gate Set for Itinerant Microwave Photons

Large-scale quantum computing will likely employ distributed network architectures in which photons, the fundamental quantum units of light, act as mobile carriers of quantum information to communicate between network nodes. Engineering the necessary interactions between two photons is challenging at optical frequencies but is more readily achievable at microwave frequencies. Here, we experimentally demonstrate an entangling two-qubit gate—a fundamental building block of any quantum algorithm—using controlled interactions between itinerant microwave photons.Our setup makes use of the strong coupling between microwave photons and superconducting circuit devices. We use one device to generate single-photon wave packets acting as flying qubits, which are then funneled to a second superconducting circuit engineered to perform one of two operations on the received qubit. The receiving circuit can absorb, act on, and reemit a qubit (a single-qubit gate) or it can shift the phase of a qubit depending on the state of another (a controlled-phase gate). These operations represent a universal set of quantum gates of microwave-photon qubits.We envision this setup being used to generate larger entanglement among many microwave-photon qubits and finding a wide range of applications in superconducting quantum networks.ISSN:2160-330

Microwave Quantum Link between Superconducting Circuits Housed in Spatially Separated Cryogenic Systems

Superconducting circuits are a strong contender for realizing quantum computing systems and are also successfully used to study quantum optics and hybrid quantum systems. However, their cryogenic operation temperatures and the current lack of coherence-preserving microwave-to-optical conversion solutions have hindered the realization of superconducting quantum networks spanning different cryogenic systems or larger distances. Here, we report the successful operation of a cryogenic waveguide coherently linking transmon qubits located in two dilution refrigerators separated by a physical distance of five meters. We transfer qubit states and generate entanglement on demand with average transfer and target state fidelities of 85.8% and 79.5%, respectively, between the two nodes of this elementary network. Cryogenic microwave links provide an opportunity to scale up systems for quantum computing and create local area superconducting quantum communication networks over length scales of at least tens of meters. © 2020 American Physical Society.ISSN:0031-9007ISSN:1079-711

Loophole-free Bell inequality violation with superconducting circuits

Abstract Superposition, entanglement and non-locality constitute fundamental features of quantum physics. The fact that quantum physics does not follow the principle of local causality can be experimentally demonstrated in Bell tests performed on pairs of spatially separated, entangled quantum systems. Although Bell tests, which are widely regarded as a litmus test of quantum physics, have been explored using a broad range of quantum systems over the past 50 years, only relatively recently have experiments free of so-called loopholes succeeded. Such experiments have been performed with spins in nitrogen–vacancy centres, optical photons and neutral atoms. Here we demonstrate a loophole-free violation of Bell’s inequality with superconducting circuits, which are a prime contender for realizing quantum computing technology. To evaluate a Clauser–Horne–Shimony–Holt-type Bell inequality, we deterministically entangle a pair of qubits and perform fast and high-fidelity measurements along randomly chosen bases on the qubits connected through a cryogenic link spanning a distance of 30 metres. Evaluating more than 1 million experimental trials, we find an average S value of 2.0747 ± 0.0033, violating Bell’s inequality with a P value smaller than 1e-108 . Our work demonstrates that non-locality is a viable new resource in quantum information technology realized with superconducting circuits with potential applications in quantum communication, quantum computing and fundamental physics

Relational ties or customized contracts? An examination of alternative governance choices in China

As business transactions become more complex in China – an increasingly market-driven economy – are managers more likely to employ relational ties or contracts? Consistent with the view that personal institutions govern transactions in China, our analysis of 361 buyer–supplier exchanges indicates that managers rely more on relational ties as asset specificity and uncertainty increase. We also find some support that impersonal institutions govern market transactions: as uncertainty increases, managers craft more customized contracts. Surprisingly, there is no association between contracts and asset specificity. These results hold for both local and foreign firms. Journal of International Business Studies (2008) 39, 526–534. doi:10.1057/palgrave.jibs.8400363

Genetic distance, international experience and the performance of cross-border R&D for EMNEs

Cross-border R&D can contribute to the enhancement of independent innovation capabilities of emerging markets multinational enterprises (EMNEs) by benefiting from knowledge management. However, scant research exists examining the location impact of cross-border R&D for EMNEs on performance implications. This paper fills this important theoretical gap by building upon the literature of genetic distance in connection with knowledge management. We use a panel data of Chinese high-tech listed companies to empirically examine the impact of genetic distance on the performance of cross-border R&D and the role played by international experience. Our results reveal a positive relationship between genetic distance and the performance of cross-border R&D. Importantly, we highlight the motivation for cross-border R&D of EMNEs to acquire technical knowledge magnifies the positive effects of genetic distance and performance. Furthermore, our analysis indicates that international experience significantly enhanced the positive effect of genetic distance on cross-border R&D performance. We conclude this paper by discussing theoretical contributions to genetic distance, international management and knowledge management, as well as practical implications for cross-border R&D of EMNEs