Resonant Quantum Search with Monitor Qubits

We present an algorithm for the generalized search problem (searching $k$ marked items among $N$ items) based on a continuous Hamiltonian and exploiting resonance. This resonant algorithm has the same time complexity $O(\sqrt{N/k})$ as the Grover algorithm. A natural extension of the algorithm, incorporating auxiliary "monitor" qubits, can determine $k$ precisely, if it is unknown. The time complexity of our counting algorithm is $O(\sqrt{N})$, similar to the best quantum approximate counting algorithm, or better, given appropriate physical resources.Comment: 12 pages, 1 figur

Nationality Classification Using Name Embeddings

Nationality identification unlocks important demographic information, with many applications in biomedical and sociological research. Existing name-based nationality classifiers use name substrings as features and are trained on small, unrepresentative sets of labeled names, typically extracted from Wikipedia. As a result, these methods achieve limited performance and cannot support fine-grained classification. We exploit the phenomena of homophily in communication patterns to learn name embeddings, a new representation that encodes gender, ethnicity, and nationality which is readily applicable to building classifiers and other systems. Through our analysis of 57M contact lists from a major Internet company, we are able to design a fine-grained nationality classifier covering 39 groups representing over 90% of the world population. In an evaluation against other published systems over 13 common classes, our F1 score (0.795) is substantial better than our closest competitor Ethnea (0.580). To the best of our knowledge, this is the most accurate, fine-grained nationality classifier available. As a social media application, we apply our classifiers to the followers of major Twitter celebrities over six different domains. We demonstrate stark differences in the ethnicities of the followers of Trump and Obama, and in the sports and entertainments favored by different groups. Finally, we identify an anomalous political figure whose presumably inflated following appears largely incapable of reading the language he posts in.Comment: 10 pages, 9 figures, 4 table, accepted by CIKM 2017, Demo and free API: www.name-prism.co

Scalable and Flexible Classical Shadow Tomography with Tensor Networks

Classical shadow tomography is a powerful randomized measurement protocol for predicting many properties of a quantum state with few measurements. Two classical shadow protocols have been extensively studied in the literature: the single-qubit (local) Pauli measurement, which is well suited for predicting local operators but inefficient for large operators; and the global Clifford measurement, which is efficient for low-rank operators but infeasible on near-term quantum devices due to the extensive gate overhead. In this work, we demonstrate a scalable classical shadow tomography approach for generic randomized measurements implemented with finite-depth local Clifford random unitary circuits, which interpolates between the limits of Pauli and Clifford measurements. The method combines the recently proposed locally-scrambled classical shadow tomography framework with tensor network techniques to achieve scalability for computing the classical shadow reconstruction map and evaluating various physical properties. The method enables classical shadow tomography to be performed on shallow quantum circuits with superior sample efficiency and minimal gate overhead and is friendly to noisy intermediate-scale quantum (NISQ) devices. We show that the shallow-circuit measurement protocol provides immediate, exponential advantages over the Pauli measurement protocol for predicting quasi-local operators. It also enables a more efficient fidelity estimation compared to the Pauli measurement.Comment: 15 pages + 1 page appendix, 10 figure

Measurement-Induced Criticality is Tomographically Optimal

We develop a classical shadow tomography protocol utilizing the randomized measurement scheme based on hybrid quantum circuits, which consist of layers of two-qubit random unitary gates mixed with single-qubit random projective measurements. Unlike conventional protocols that perform all measurements by the end of unitary evolutions, our protocol allows measurements to occur at any spacetime position throughout the quantum evolution. We provide a universal classical post-processing strategy to approximately reconstruct the original quantum state from intermittent measurement outcomes given the corresponding random circuit realizations over repeated experiments. We investigated the sample complexity for estimating different observables at different measurement rates of the hybrid quantum circuits. Our result shows that the sample complexity has an optimal scaling at the critical measurement rate when the hybrid circuit undergoes the measurement-induced transition.Comment: 6 pages, 4 figures + 13 pages appendice

Phase-fluctuation Induced Time-Reversal Symmetry Breaking Normal State

Spontaneous time-reversal symmetry (TRS) breaking plays an important role in studying strongly correlated unconventional superconductors. When the superconducting gap functions with different pairing symmetries compete, an Ising ($Z_2$) type symmetry breaking occurs due to the locking of the relative phase $\Delta\theta_{12}$ via a second order Josephson coupling. The phase locking can take place even in the normal state in the phase fluctuation regime before the onset of superconductivity. If $\Delta\theta_{12}=\pm\frac{\pi}{2}$, then TRS is broken, otherwise, if $\Delta\theta_{12}=0$, or, $\pi$, rotational symmetry is broken leading to a nematic state. In both cases, the order parameters possess a 4-fermion structure beyond the scope of mean-field theory. We employ an effective two-component $XY$-model assisted by a renormalization group analysis to address this problem. In addition, a quartetting, or, charge-``4e", superconductivity can also occur above $T_c$. Monte-Carlo simulations are performed and the results are in a good agreement with the renormalization group analysis. Our results provide useful guidance for studying novel symmetry breakings in strongly correlated superconductors.Comment: 4+ pages, 3 figures. References are added. Supplementary Material is updated. Comments are welcom

Solitary pulmonary mass in a patient with a history of lymphoma: a case report

INTRODUCTION: With the progress made in treatments, the survival rate for patients with malignant lymphoma in the last 30 years has significantly improved. However, the risk of experiencing a second primary malignancy or other disease has increased significantly. CASE PRESENTATION: A 44-year-old Mongolian man with a large mass in his right lower abdomen was admitted to our hospital 15 years previously. The mass was removed, and confirmed via pathological examination to be a malignant B-cell lymphoma in the appendix and distal small bowel. Post-operative chemotherapy with standard cyclophosphamide, hydroxydaunomycin, vincristine (Oncovin®) and prednisolone regimen was given for six cycles. No obvious recurrence was detected over the following 12 years. Subsequently, a mass in the right lung was found on a regular X-ray follow-up; our patient did not report chills, fever or cough. Chest computed tomography and positron emission tomography scans confirmed the mass. A primary lung carcinoma was considered to be the most likely diagnosis. However, after an exploratory thoracotomy and right upper lobectomy was performed a pathological examination of tissue samples demonstrated a lung cryptococcal granuloma, with positive staining for periodic acid Schiff and periodic acid-silver metheramine. CONCLUSIONS: Compared to the normal population, second primary malignancy (in particular leukaemia and lung cancer) in patients with malignant lymphoma during their long-term survival has been seen occasionally. However, other diagnoses should also be considered such as pulmonary cryptococcosis. Other than computed-tomography-guided needle biopsy, surgery for some patients is a much more appropriate choice, which could also help attain correct diagnosis and treatment