Japan's central bank started to pursue a policy of quantitative easing in 2001.  It moved off of the "zero-interest rate" policy after 5 years, but then the global economic crisis hit, and rates went down again.  Now, it is continuing to push monetary policy as a means of fighting deflation in the world's second largest economy.  Hiroko Tabuchi has the story in today's New York Times:

Central banks around the world have in recent weeks mulled rolling back stimulus steps put in place during the global economic crisis, gradually shrinking excess liquidity in their banking systems. The U.S. Federal Reserve said Tuesday it will let a mortgage-security purchase program expire at the end of March.

But in Japan — where prices have remained sluggish amid a lackluster recovery from its worst recession since World War II — the government has urged monetary authorities to further stimulate the economy by flooding the banking sector with cash.

Japan is also leaning on monetary policy because its public debt load, the highest among industrialized countries, makes it reluctant to spend more money on public works projects and other government stimulus programs.

Read Japan Eases Monetary Policy to Fight Deflation here.