How to use indexed=false in JDO?

Question

I have a data class (in Google app Engine, JDO) as

@PersistenceCapable
public class Employee {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;

    @Persistent
    private String firstName;

    @Persistent
    private String lastName;

    @Persistent
    private Date hireDate;
}

I don't want hireDate to be indexed, how can i do it?