Rabi Oscillations in Systems with Small Anharmonicity

When a two-level quantum system is irradiated with a microwave signal, in resonance with the energy difference between the levels, it starts Rabi oscillation between those states. If there are other states close, in energy, to the first two, the Rabi signal will also induce transition to those. Here, we study the probability of transition to the third state, in a three-level system, while a Rabi oscillation between the first two states is performed. We investigate the effect of pulse shaping on the probability and suggest methods for optimizing pulse shapes to reduce transition probability.Comment: 7 pages, 7 figure

Welcome to the Dark Side - Hedge Fund Attrition and Survivorship Bias over the period 1994-2001

Hedge funds exhibit a high rate of attrition that has increased substantially over time. Using data over the period 1994-2001, we show that lack of size, lack of performance and an increasingly aggressive attitude of old and new fund managers alike are the main factors behind this. Although attrition is high, survivorship bias in hedge fund data is quite modest, which reflects the relatively small difference in performance between surviving and defunct funds. Concentrating on survivors only will overestimate the average hedge fund return by around 2% per annum. For small, young, and leveraged funds, however, the bias can be as high as 4-6%. We also find significant survivorship bias in estimates of the standard deviation, skewness and kurtosis of individual hedge fund returns. When not corrected for, this will lead investors to seriously overestimate the benefits of hedge funds. We find fund of funds attrition to be much lower than for hedge funds. Combined with a small difference in performance between surviving and defunct funds of funds, this yields relatively low survivorship bias estimates for funds of funds.

Does Microcredit Reach the Poor and Vulnerable? Evidence from Northern Bangldesh.

The Grameen Bank's success in Bangladesh has made microcredit the hot new idea for reducing poverty. This paper uses panel data from two Bangladeshi villages to test if loan recipients are poorer and more vulnerable than non-recipients. Poverty is measured by levels of consumption. Vulnerablitiy is measured as fluctuations in consumption (associated with inefficient risk sharing). We find that loan recipients are poorer than non-recipients in both villages, but are more vulnerable than non-recipients only in the richer and more diversified village. Though microcredit programs target the landless, there is substantial leakage to the landed. Landlessness is not significangly associated with either poverty or vulnerablitiy, but female headship is. Female headed households may be a more appropriate target group for anti-poverty credit programs.POVERTY ; RISK ; ECONOMIC GROWTH