School of Physics & Material Science,Anhui University,Hefei 230039,China;
Department of Physics,Anqing Teachers College,Anqing 246011,China;
School of Physics & Material Science,Anhui University,Hefei 230039,China;
School of Physics & Material Science,Anhui University,Hefei 230039,China;
entanglement concentration; W state; linear optical elements;