\version "2.11.34"

stemExtend = {
  \once \override Stem #'length = #10
  \once \override Stem #'cross-staff = ##t
}
noFlag = \once \override Stem #'flag-style = #'no-flag
\new PianoStaff <<
  \new Staff {
    \stemDown \stemExtend
    f'4
    \stemExtend \noFlag
    f'8
    \stemExtend \noFlag
    b'8
    \stemExtend \noFlag
    d''8
  }
  \new Staff {
    \clef bass
    a4 a8 g8 e8
  }
>>