However, at the moment only works on x86 Intel-based processors.
The new emulator will allow app developers to optimize their software for 64-bit versions of Android L.
Google revealed that app creators will be able to access a larger amount of addressable memory space with 64-bit support, along with a bigger number of registers and new instruction sets. Apps built using Java will automatically access all those cool features, but apps made using the Android NDK will take some additional optimization to achieve full 64-bit support.
The vast majority of Android devices use ARM-based processors but there’s no word on when a 64-bit emulator will be released for those kinds of CPUs.
Via Android Central