Communication Complexity Lower Bounds by Polynomials

The quantum version of communication complexity allows the two communicating parties to exchange qubits and/or to make use of prior entanglement (shared EPR-pairs). Some lower bound techniques are available for qubit communication complexity, but except for the inner product function, no bounds are known for the model with unlimited prior entanglement. We show that the log-rank lower bound extends to the strongest model (qubit communication + unlimited prior entanglement). By relating the rank of the communication matrix to properties of polynomials, we are able to derive some strong bounds for exact protocols. In particular, we prove both the "log-rank conjecture" and the polynomial equivalence of quantum and classical communication complexity for various classes of functions. We also derive some weaker bounds for bounded-error quantum protocols.Comment: 16 pages LaTeX, no figures. 2nd version: rewritten and some results adde

Quantum Zero-Error Algorithms Cannot be Composed

We exhibit two black-box problems, both of which have an efficient quantum algorithm with zero-error, yet whose composition does not have an efficient quantum algorithm with zero-error. This shows that quantum zero-error algorithms cannot be composed. In oracle terms, we give a relativized world where ZQP^{ZQP}\=ZQP, while classically we always have ZPP^{ZPP}=ZPP.Comment: 7 pages LaTeX. 2nd version slightly rewritte

Explaining Inefficient Policy Instruments

Distorted incentives, agricultural and trade policy reforms, national agricultural development, Agricultural and Food Policy, International Relations/Trade, F13, F14, Q17, Q18,

Lower Bounds for Quantum Search and Derandomization

We prove lower bounds on the error probability of a quantum algorithm for searching through an unordered list of N items, as a function of the number T of queries it makes. In particular, if T=O(sqrt{N}) then the error is lower bounded by a constant. If we want error <1/2^N then we need T=Omega(N) queries. We apply this to show that a quantum computer cannot do much better than a classical computer when amplifying the success probability of an RP-machine. A classical computer can achieve error <=1/2^k using k applications of the RP-machine, a quantum computer still needs at least ck applications for this (when treating the machine as a black-box), where c>0 is a constant independent of k. Furthermore, we prove a lower bound of Omega(sqrt{log N}/loglog N) queries for quantum bounded-error search of an ordered list of N items.Comment: 12 pages LaTeX. Submitted to CCC'99 (formerly Structures

BIOFUELS AND LEAKAGES IN THE FUEL MARKET

Leakage in the fuel market differs, depending on whether ethanol production is determined by a tax credit or consumption mandate. Two components of market leakage are distinguished: domestic and international. Leakage with both a tax credit and a consumption mandate depends on market elasticities and consumption/production shares, with the former having a bigger impact. Leakage is also more sensitive to changes in market supply and demand elasticities in the country not introducing biofuels. Although positive with a tax credit, market leakage can be negative with a consumption mandate, meaning that one gallon of ethanol can replace more than a gallon of gasoline. We also show that being a small country biofuels producer does not necessarily mean that leakage for this country is 100 percent. Our numerical estimates show that one gallon of ethanol replaces approximately 0.2-0.3 gallons of gasoline in the U.S.Agricultural and Food Policy, Crop Production/Industries, Environmental Economics and Policy, International Relations/Trade, Resource /Energy Economics and Policy,

On the regulation of unobserved emissions

Regulation of nonpoint source pollution often relies in one way or another on policy instruments based on ambient indicators. For well-known reasons, enforcement of ambient-based policies is, at best, limited. If no individual choices or actions are observed, than ambient-based regulation might be the only feasible approach. Often, some relevant individual indicators, such as output or certain inputs, are observable. For such cases, we offer a regulation mechanism that does away with ambient indicators. The mechanism implements the optimal output-abatement-emission allocation and gives rise to the full information outcome when the social cost of transfers is nil. Special attention is given to the regulation of (unobserved) abatement.Nonpoint source pollution, abatement, asymmetric information, regulation mechanism, implementation., Environmental Economics and Policy,

Better Non-Local Games from Hidden Matching

We construct a non-locality game that can be won with certainty by a quantum strategy using log n shared EPR-pairs, while any classical strategy has winning probability at most 1/2+O(log n/sqrt{n}). This improves upon a recent result of Junge et al. in a number of ways.Comment: 11 pages, late

THE CANADA- U.S. TRADE DISPUTES ON DAIRY AND POULTRY: A GOOD EXAMPLE

International Relations/Trade,

DISENTANGLING THE PRODUCTION AND EXPORT CONSEQUENCES OF DIRECT FARM INCOME PAYMENTS

This paper formalizes the production and export consequences of direct farm payments. Taxpayer financed direct payments distort exit and production incentives, while consumer financed subsidies also imply that the risks of domestic and export production differ. Welfare decompostion and empirical calibration illustrate the potential for import barriers to cross-subsidize exports.Agricultural and Food Policy, International Relations/Trade,

An Econometric Model of the European Economic Community's Wheat Sector

Crop Production/Industries,