Ben Bernanke introduced a first round of quantitative easing during the worst of the financial crisis, as global markets tumbled and liquidity was sucked out of the system. Quantitative easing is an unorthodox application of monetary policy by which a central bank, in this case the Federal Reserve, loosens monetary policy further after having dropped the Federal Funds rate to the zero range. This is done by purchasing longer-term assets, such as 10 year Treasury bonds, in order to push down interest rates further down the yield curve.Quantitative easing, or QE, came into prominence after Japan attempted to prop up its economy after a massive financial and economic crash during the 1990s. Japan entered what is commonly referred to as the "Lost Decade," where not even QE managed to boost output substantially.