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"Smart, Scott"
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Quantum simulation of molecules without fermionic encoding of the wave function
Molecular simulations generally require fermionic encoding in which fermion statistics are encoded into the qubit representation of the wave function. Recent calculations suggest that fermionic encoding of the wave function can be bypassed, leading to more efficient quantum computations. Here we show that the two-electron reduced density matrix (2-RDM) can be expressed as a unique functional of the unencoded N -qubit-particle wave function without approximation, and hence, the energy can be expressed as a functional of the 2-RDM without fermionic encoding of the wave function. In contrast to current hardware-efficient methods, the derived functional has a unique, one-to-one (and onto) mapping between the qubit-particle wave functions and 2-RDMs, which avoids the over-parametrization that can lead to optimization difficulties such as barren plateaus. An application to computing the ground-state energy and 2-RDM of H 4 is presented.
Journal Article
Conservatism and international IPO underpricing
We study the impact of country-level accounting conservatism on international IPO underpricing. Examining 13,285 IPOs from 36 countries, we find that IPOs are underpriced less in countries in which existing public firms practice more accounting conservatism. The link between conservatism and underpricing is robust to alternative measures of conservatism, country mean regressions, sample country exclusions, and endogenous treatment models. Consistent with the hypothesis that conservatism reduces underpricing by mitigating the impact of information asymmetries, we find that higher country-level conservatism is associated with lower country-level PIN values and that the negative relation between conservatism and underpricing is strongest for IPOs involving small firms in which information asymmetries are likely to be high. Lastly, we find evidence that legal origin, a factor linked to the practice of conservatism, influences the relations between underpricing and conservatism.
Journal Article
Earnings Quality and International IPO Underpricing
This study examines the impact of country-level earnings quality on IPO underpricing. Examining 10,783 IPOs from 37 countries, we find that IPOs are underpriced less in countries where public firms produce higher quality earnings information. This finding persists after controlling for other deal- and country-specific factors that affect IPO underpricing, and it is driven neither by the large and relatively transparent markets in the U.S. and U.K. nor by the relatively opaque Japanese market. The impact of low earnings quality on underpricing is partially offset by the use of a top-tier underwriter.
Journal Article
IPO Underpricing and International Corporate Governance
It is well established that a link exists between a country's legal system and the size, liquidity, and value of its capital markets. We study how differences in country-level governance affect the underpricing of initial public offerings (IPOs). Examining 4462 IPOs across 29 countries from 2000 to 2004, we find the surprising result that underpricing is higher in countries with corporate governance that strengthens the position of investors relative to insiders. We conjecture that when countries give outsiders more influence, IPO issuers underprice more to generate excess demand for the offer, which in turn leads to greater ownership dispersion and reduces outsiders' incentives to monitor the behavior of corporate insiders. In other words, underpricing is a cost that insiders pay to maintain control in countries with legal systems designed to empower outsiders. Consistent with this control motivation for underpricing, we find that underpricing has a negative association with post-IPO outside blockholdings and a positive association with private control benefits. In addition, firms whose insiders are entrenched either by majority ownership or by dual-class structures do not underprice more in countries with better governance. In these firms the ownership structure protects managers from outside influence, eliminating the incentive to increase outside ownership dispersion through underpricing.
Journal Article
Relaxation of stationary states on a quantum computer yields a unique spectroscopic fingerprint of the computer’s noise
Quantum computing has the potential to revolutionize computing, but its significant sensitivity to noise requires sophisticated error correction and mitigation. Traditionally, noise on the quantum device is characterized directly through qubit and gate measurements, but this approach has drawbacks in that it does not adequately capture the effect of noise on realistic multi-qubit applications. In this paper, we simulate the relaxation of stationary quantum states on a quantum computer to obtain a unique spectroscopic fingerprint of the computer’s noise. In contrast to traditional approaches, we obtain the frequency profile of the noise as it is experienced by the simulated stationary quantum states. Data from multiple superconducting-qubit IBM processors show that noise generates a bath within the simulation that exhibits both colored noise and non-Markovian behavior. Our results provide a direction for noise mitigation but also suggest how to use noise for quantum simulations of open systems.
Quantifying, controlling, and correcting noise related errors is one of the current challenges in quantum computing. Here, the authors study the time dependence of the relaxation of a stationary state simulated on a quantum computer, and show that such spectroscopic signature is unique and can be used to characterize the noise on individual quantum computers.
Journal Article
A Clinically Relevant Functional Model of Type-2 Cardio-Renal Syndrome with Paraventricular Changes consequent to Chronic Ischaemic Heart Failure
Cardiorenal syndrome,
de novo
renal pathology arising secondary to cardiac insufficiency, is clinically recognised but poorly characterised. This study establishes and characterises a valid model representative of Type 2 cardiorenal syndrome. Extensive permanent left ventricular infarction, induced by ligation of the left anterior descending coronary artery in Lewis rats, was confirmed by plasma cardiac troponin I, histology and cardiac haemodynamics. Renal function and morphology was assessed 90-days post-ligation when heart failure had developed. The involvement of the paraventricular nucleus was investigated using markers of inflammation, apoptosis, reactive oxygen species and of angiotensin II involvement. An extensive left ventricular infarct was confirmed following coronary artery ligation, resulting in increased left ventricular weight and compromised left ventricular diastolic function and developed pressure. Glomerular filtration was significantly decreased, fractional excretion of sodium and caspase activities were increased and basement membrane thickening, indicating glomerulosclerosis, was evident. Interestingly, angiotensin II receptor I expression and reactive oxygen species levels in the hypothalamic paraventricular nucleus remained significantly increased at 90-days post-coronary artery ligation, suggesting that these hypothalamic changes may represent a novel, valuable pharmacological target. This model provides conclusive morphological, biochemical and functional evidence of renal injury consequent to heart failure, truly representative of Type-2 cardiorenal syndrome.
Journal Article
Industrial Diversification and Underpricing of Initial Public Offerings
The initial public offerings (IPOs) of diversified firms, those reporting more than one business segment at the time they go public, experience less underpricing than do IPOs by focused issuers.We explore two explanations for this phenomenon. Diversification may benefit IPO firms by reducing information asymmetries and therefore, lowering underpricing costs. Alternatively, high quality focused firms may be signaling their value by underpricing their shares to a greater degree. Though we find at least some evidence consistent with each explanation, a majority of the evidence favors signaling.
Journal Article
Acquisition Activity and IPO Underpricing
We propose an \"M&A activity\" hypothesis as a partial explanation for initial public offering (IPO) underpricing. When going public during active corporate control markets, managers may take actions to safeguard their control. In support of this conjecture, we find thatpre-IPO M&A activity directly explains IPO underpricing. We also find that underpricing and ownership dispersion are positively correlated, as are ownership dispersion and the probability of remaining independent. Considering the possibility that some managers take their firms public to be acquired, we find that the positive link between M&A activity and underpricing is not robust for firms that are viewed as likely targets.
Journal Article