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In this work, we present a protocol for comparing the performance of arbitrary quantum processes executed on spatially or temporally disparate quantum platforms using Local Operations and Classical Communication (LOCC). The protocol involves sampling local unitary operators, which are then communicated to each platform via classical communication to construct quantum state preparation and measurement circuits. Subsequently, the local unitary operators are implemented on each platform, resulting in the generation of probability distributions of measurement outcomes. The max process fidelity is estimated from the probability distributions, which ultimately quantifies the relative performance of the quantum processes. Furthermore, we demonstrate that this protocol can be adapted for quantum process tomography. We apply the protocol to compare the performance of five quantum devices from IBM and the "Qianshi" quantum computer from Baidu via the cloud. Remarkably, the experimental results reveal that the protocol can accurately compare the performance of the quantum processes implemented on different quantum computers, requiring significantly fewer measurements than those needed for full quantum process tomography. We view our work as a catalyst for collaborative efforts in cross-platform comparison of quantum computers.

In this work, we propose a two-stage procedure to systematically address quantum noise inherent in quantum measurements. The idea behind it is intuitive: we first detect and then eliminate quantum noise so that the classical noise assumption is satisfied and measurement error mitigation works. In the first stage, inspired by coherence witness in the resource theory of quantum coherence, we design an efficient method to detect quantum noise. It works by fitting the difference between two measurement statistics to the Fourier series, where the statistics are obtained using maximally coherent states with relative phase and maximally mixed states as inputs. The fitting coefficients quantitatively benchmark quantum noise. In the second stage, we design various methods to eliminate quantum noise, inspired by the Pauli twirling technique. They work by executing randomly sampled Pauli gates before the measurement device and conditionally flipping the measurement outcomes in such a way that the effective measurement device contains only classical noise. We demonstrate the feasibility of the two-stage procedure numerically on Baidu Quantum Platform. Remarkably, the results show that quantum noise in measurement devices is significantly suppressed, and the quantum computation accuracy is substantially improved. We highlight that the two-stage procedure complements existing measurement error mitigation techniques, and they together form a standard toolbox for manipulating measurement errors in near-term quantum devices., Comment: 24 pages, 5 figures, comments are welcome!

Cereal/legume intercropping can achieve overyielding and higher N use efficiency through enhanced nitrogen (N) fixation by legumes and nitrogen transfer to cereals. However, the extent to which root morphology contributes to N fixation and transfer is unclear. We conducted a two-factorial greenhouse experiment to quantify the N fixation, transfer and root morphology characteristics of the maize/alfalfa intercropping system in two consecutive years using the 15N-urea leaf labelling method, and combining two N levels with three root barriers. Irrespective of the N application level, compared with plastic sheet separation (PSS), no separation (NS) and nylon mesh separation (NNS) significantly increased the total biomass (36%) and total N content (28%), while the N fixation rate also sharply increased by 75 to 134%, and the amount of N transferred with no root barrier was 1.24–1.42 times greater than that with a mesh barrier. N application could inhibit N fixation and transfer in a maize/alfalfa intercropping system. Redundancy analysis (RDA) showed that the crown root dry weight (CRDW) of maize and lateral root number (LRN) of alfalfa showed the strongest associations with N fixation and transfer. Results highlight that in maize/alfalfa intercropping systems, root contact is important because it enhanced N fixation and transfer. Root contact is strongly influenced by root morphology plasticity responses to competition and thereby achieving a greater yield.

This thesis consists of three related essays that investigate the internationalization of entrepreneurial firms. The essays investigate the motivation of entrepreneurial firms to internationalize, the learning mechanisms during the internationalization process and firm performance post-internationalization. I build on the behavioural theory of the firm and the learning theory to explain internationalization of entrepreneurial firms. In the first essay, I explain the motivation of entrepreneurial firms to internationalize. I propose that internationalization represents a significant strategic change for an entrepreneurial firm. Following the literature on the behavioural theory of the firm, I argue that firms engage in internationalization when they encounter difficulties in the domestic market. I posit that firms that are performing below their aspiration level in domestic markets are more likely to internationalize (entry hypothesis). I further posit that such underperforming firms will compete in locations that are more culturally distant than firms that are performing above their aspiration level (culture distance hypothesis). My entry hypothesis is supported and culture distance hypothesis is not. In the second essay, I explain how entrepreneurial firms with no previous international experience learn in the international market. I draw on the learning theory and the experience spillover effects to predict firm's learning behaviour. I argue that there are essential similarities between managing a foreign alliance and managing international expansion. I posit that firms can transfer their experience at managing a foreign alliance before international entry to managing international market once they made the entry. I find empirical support for such transfer effect. In the third essay, I focus on learning and performance effect postinternationalization. I argue that entrepreneurial firms that have entered international markets face competing learning demands. The competing demands originate from the needs to developing core capability inside the firm and from the need to adjust to a new environment outside the firm. Excelling on both types of learning will lead to faster international growth. But when firms cannot achieve both simultaneously, those that use their international exposure to facilitate core capability development internally will achieve faster international growth.