Yes,

You should have good knowledge of brokers / stock market API, and a long experience dealing with them to fully understand arbitrage oportunities, market data and financial products they offer.

Execution problems, liquidity and sometimes regulation take un important place during the trading days.

You also need to get some knowledge of hedging and market risk management.

For the jobs opportunities I 've seen Senior Quant trader positions at 1 to 2M$ in hedge fund industry (if you want to work for others, but at this point you'd better build your own fund no?).

To be selected you need to be able to discuss strategies and market data and to be used to financial trading concepts, showing you 've already tested some strategies, tryed to hedge risk... It's a lot of work I know. Focus yourself on a unique strategy (Index arbitrage for example) and try to build it, find bibliography, reasearch articles and write one on your own. Try to meet people from this business, go to conferences. That can make the difference !

Best whishes ...